Kline Innovation exhaust for the Porsche 991 Turbo and Turbo S: options, legality and used-system checks
Owners of the 991 Turbo and Turbo S (2013-2019) sometimes look for a used Kline Innovation exhaust, either to fit one or to replace a worn set. Because the system comes in several configurations, the main task is working out exactly which one a seller is offering and whether it is legal for the road where you live. This page summarises what the maker and its retailers say. Specifications below come from Kline and from retailers selling Kline products, and have not been independently measured.
In this guide
Who is Kline Innovation?
Kline Innovation is a Romanian exhaust maker (a retailer describes it as Bucharest-based) that produces Inconel and stainless exhaust systems for Porsche, Ferrari, Lamborghini, Audi, BMW, McLaren, Mercedes-AMG and others. Its own website lists a wide Porsche range from the 718 to the 992 and says it has TUV certification.1 One retailer describes the company as relatively new to the supercar exhaust market, building on earlier 996 and 997 Turbo systems.2
What is offered for the 991 Turbo?
Retailer listings and Kline's own 991 Turbo Exclusive page describe a turbo-back system, meaning everything behind the turbochargers. The listed features are an x-pipe, tuned silencers, and an "overflow" secondary tailpipe intended to keep low-rpm noise down while opening up at high rpm.3
| Choice | Options listed |
|---|---|
| Material | 304 stainless steel or Inconel 625 (titanium silencer also listed on Kline's page) |
| Catalysts | None (race pipes), 100-cell, or 200-cell high-flow catalysts |
| Silencers | Regular, a TUV version, and a race version, per a retailer |
| Weight | Kline lists about 7.5 kg in Inconel and 14 kg in stainless with 200-cell catalysts |
| Fitment | 991.1 and 991.2 Turbo and Turbo S, per retailers |
Kline's page quotes gains of about 38 hp without catalysts, 20 hp with 100-cell and 16 hp with 200-cell catalysts, and a retailer cites earlier preliminary dyno estimates for the catless version.32 These are manufacturer figures, with no independent test behind them here. A retailer's 991.2 Turbo S listing notes that manifolds and carbon fibre tips shown in photos are not part of the standard package, so check what a used set actually includes.4
Installation and fitment notes
Retailers describe the systems as bolt-on and direct fit. Details to confirm before buying:
- 991.1 versus 991.2. Retailers list both generations, but the exact part is generation-specific. Ask for the model year and whether the seller has the matching hardware.
- Turbo versus Turbo S, and Exclusive Series. Kline has a dedicated listing for the Turbo Exclusive, so confirm that your car is covered.3
- Tuning. Removing the catalysts and fitting free-flowing pipes on a modern turbocharged engine changes exhaust flow, and many owners add an engine software calibration afterwards. The materials reviewed do not specify whether a tune is required, so ask Kline, the retailer or a Porsche tuner.
- Fitting. Have it fitted by a shop familiar with the 991 Turbo, since the hardware is hot, heavy and requires correct alignment of the hangers and tips.
Sound and legality
- Noise. Kline describes the system as having no drone at cruise and a raised-pitch howl at high rpm.3 Subjective, and owner experience varies by configuration; the race silencers will be louder than the TUV ones. Noise limits for road vehicles vary by country and region, and some inspection regimes check noise. The existence of a TUV-compliant version, per retailers, points to the regulated markets the company designs for, but a TUV mark does not guarantee compliance for your jurisdiction or the exact car.
- Catalytic converters in the United States. A 1991 EPA letter and fact sheet states that, under the 1990 Clean Air Act Amendments, a pipe replacing the section where the catalytic converter belongs is illegal and any work in that area must include proper converter replacement. The same amendments extended the tampering prohibition to private individuals and to the sale and installation of parts that principally bypass or defeat emission controls.5 The EPA has also announced settlements with aftermarket companies for exhaust systems that bypass catalytic converters.6 The "de-cat" or race-pipe variants are therefore hard to square with US road use, and may not pass emissions inspections in other places either. If the car is registered for road use, the catalyst versions are the safer choice; check your local rules.
- Warranty and insurance. A modified exhaust can affect factory warranty claims and insurance in some places. Confirm with your dealer and insurer.
What to check on a used system
- Which variant it is. Material (stainless or Inconel), catalyst or race pipes, silencer type, and the generation it was made for. Ask for photos of any markings and for the original invoice or order details.
- Completeness. Pipes, silencers, tips, clamps, gaskets, hangers and any bracketry. Confirm whether manifolds or carbon tips are included.
- Condition. Inconel and stainless can still crack at welds and flanges. Look for flange warping, cracks, dents, heat marks on the silencers, and damaged threads. If catalysts are fitted, ask about mileage and any misfire history.
- Mounting points and clearance. Check for rubbing marks that suggest it was fitted badly.
- Paperwork. Ask whether any certification documents (such as a TUV document) come with it, as those are useful in inspection regimes that ask for them.
- Provenance. Kline's site mentions a dealer locator; contacting the maker or an authorised dealer with the seller's details is a reasonable way to check a used system's authenticity.1 Treat any used listing's condition description as the seller's own assessment.
Compare sound clips and used-system listings fairly
A Kline 991 Turbo sound video is most useful when it identifies the car and exhaust configuration. Look for the generation, catalyst choice, silencer material and any engine tune in the description. Otherwise, the clip may demonstrate a different system from the one you are considering.
Exterior revving, a drive-by and an in-cabin recording answer different questions. Ask a seller for a cabin clip at steady cruising speed as well as acceleration footage. Recording equipment, microphone position and the road surface can change the impression, so use videos to shortlist a sound rather than to measure noise or guarantee a drone-free result.
| Seller's claim | Useful supporting evidence |
|---|---|
| "Full Kline system" | A laid-out photograph and an itemised list of every supplied section |
| "Inconel" | Original order details or identification confirmed with Kline |
| "Fits all 991 Turbos" | Confirmation of the exact configuration for your VIN or vehicle specification |
| "Road legal" | Applicable documentation for that exact configuration and your jurisdiction |
Is a 200-cell catalyst a guarantee of road approval?
No. The cell-count description identifies a product option, not a universal approval. Ask about the specific system and inspection requirements before treating that word as a compliance claim.
What should the fitted-price quote include?
Request installation labour, replacement seals and hardware where needed, alignment of the tips, and a check for leaks or contact with surrounding components. Resolve the configuration before comparing the price of a used system with a new one.
Sources and further reading
- Kline Innovation, official site: company description and Porsche range.
- Kline Innovation Exhaust System (991 Turbo), Flat 6 Motorsports: retailer listing.
- Porsche 991 Turbo Exclusive exhaust, Kline Innovation: manufacturer product page.
- Kline Innovation Turboback Exhaust System for 991.2 Turbo S, Bulletproof Automotive: retailer listing.
- Exhaust System Repair Guidelines fact sheet and cover letter, US EPA (1991)
- US EPA settles with two auto parts companies over Clean Air Act violations, US EPA