Over the years the Audi TT K04-020 turbocharger has proven to be a worthwhile upgrade on the K03 equipped mk4. Since the release of a few bolt-on K04 turbocharger kits the DIY crowd has been scouring the TT classifieds piecing together kits for less. Until now, no bolt-on downpipe has been available which allows the TT 225 K04-020 turbo and manifold to fit the mk4. Those days are over! Our 3" downpipe begins at the turbo with a CNC machined turbo flange and the tightest 3" mandrel bend possible. The remainder of our downpipe is CNC mandrel bent in one piece to add strength and eliminate unnecessary welds. A stainless steel flex section is used to absorb engine movement. After the flex section a CNC machined flange allows a 3" high-flow cat or 3" test pipe to be installed. We use Magnaflow catalytic converters for all of our downpipes. After the cat, a custom adaptor allows perfect bolt-on fitment to any aftermarket cat-back. We offer adaptors for stock sized exhausts, 2.5" and 3". The whole downpipe bolts together to ensure zero leaks and zero problems. We use triple layer graphite gaskets and grade 5 locking hardware for the tightest fit. The modular nature of our downpipe allows the user to change configurations at any time. For example, our downpipe may be purchased with a stock sized adaptor and connected to stock or any basic aftermarket cat-back exhaust. At any time a 2.5" or 3" cat-back can be installed using the appropriate adaptor. Our 3" cat-back systems are completely compatible with this downpipe allowing the possibility of a 3" turbo-back in any configuration. On race days the catalytic converter can be easily swapped for a test pipe. Our 3" downpipe is available in 6 configurations. Street series downpipes include a high-flow cat. Race series downpipes include a 3" test pipe. Each downpipe includes a cat-back adaptor. Our adaptors are available in stock size (2.15"), 2.5" and 3". Each downpipe is shipped complete with everything needed for installation. Additional adaptors, test pipe, cat section, gaskets, and hardware can be purchased separately at any time. Besides price, the biggest worry on the minds of DIY builders is fitment. Our K04 downpipe was designed using precision tooling and the OEM Audi TT 225 turbocharger and exhaust manifold. Rigorous testing was done to repeat the phenomenal fitment of our mk4 1.8T 3" downpipes. Our downpipe fits like an OEM downpipe would and an aftermarket downpipe should - no rubs, no rattles, no problems. Construction CNC mandrel bent 14 gauge aluminized steel tubing CNC machined 3/8" steel flanges 100% TIG welded construction Stainless steel braided flex section Magnaflow high flow catalytic converter (Street Series) Modular construction allows simple alteration of pipe size and cat configuration Fitment Fits 1999-2005 VW mk4 Golf, Jetta, GTI 1.8T Fits 2000-2006 Audi TT 180 FWD Fits VW New Beetle 1.8T Available in street or race configuration 2 triple layer gaskets & OEM K04 turbo gasket included 5/16" grade 5 locking hardware included Choice of 3 pipe size adaptors allow unrestricted fitment to any cat-back exhaust Important Fitment Information - Please Read BEFORE Purchasing! This downpipe has been designed to fit a specific combination of vehicle, turbo and exhaust manifold. We cannot guarantee fitment if certain components are not used. This downpipe will fit: 1999-2005 VW mk4 Golf, Jetta, GTI 1.8T 2000-2006 Audi TT 180 FWD VW New Beetle 1.8T. The following components MUST be used to ensure proper fitment: OEM Audi TT 225 Exhaust Manifold OEM Audi TT 225 K04-020, 021, or 023 Turbocharger We realize there are many aftermarket exhaust manifolds available which mimic the OEM TT 225 fitment. We have not tested any of these manifolds and cannot guarantee proper fitment with our 3" downpipe. Additionally, many knock-off K04 turbochargers are available which claim to replicate the OEM turbocharger. We cannot support or guarantee fitment of our downpipe when the proper OEM components are not used. This downpipe was designed to exactly replicate the fitment of the mk4 downpipe. It has not and will not be tested on mk2 or mk3 1.8T swap applications. Please Specify: Stock, 2.5" ot 3.0"