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The installation of an aftermarket downpipe is an integral part of the Basic Performance Upgrades (BPU). It reduces the exhaust back pressure because the pipe diameter is increased and the two catalysts are replaced, thus allowing higher boost pressures.

A downpipe for EU / US spec models typically replaces the two exhaust pipes identified here as "OEM downpipe with cat # 1" and "OEM midpipe with cat # 2" in one piece.

Required parts:

  • Downpipe suitable for EU / US Spec TT
  • Matching gasket 3-hole front / 2-hole rear
  • Screws 2x 90105-10023 for flange 2-hole rear
  • Nuts 3x 90179-10070 for flange 3-hole front
  • Nuts 2x 94180-41000 for flange 2-hole rear
  • Possibly new studs 3x 90126-10013 for front flange
  • Possibly sports / racing cat for welding

Required tools:

  • Ratchet wrench with 12 and 14 hexagon nuts, different extensions and joint
  • 12 and 14 fork or ring spanner
  • Eventually WD40 / rust remover

Expansion of serial down / mid pipe

1) Spray all screw connections with WD40 & remove the lambda probe with protective plate.

2) Loosen the midpipe and exhaust bracket bolts and remove the midpipe.


4) Unscrew downpipe bolts with cat # 1 and remove downpipe.

5) Image Flange Serial Downpipe EU / US Spec

6) Image Cat # 1 Serial Downpipe EU / US Spec

7) Flange Aftermarket Downpipe 80mm = ~ 3.15 inches

Installation aftermarket downpipe

8) Place downpipe and mount with gasket and 3x nut on flange in front of the turbos.


10) Connect downpipe with gasket and 2x bolts + nuts to the rear of the exhaust system.

11) Mount the lambda probe with protective plate on the new downpipe, finished

Info: A comparison picture between EU and J-Spec TT Downpipe

Various manufacturers of downpipes for US / EU series turbos