CTS TURBO B9.5 AUDI A4/A5/ALLROAD/Q5 2.0T HIGH-FLOW CAT (2021-2025)

Free up your 2021-2025 B9.5 Audi A4/A5/Q5 40TFSI/45TFSI 2.0T’s potential with the CTS Turbo High-Flow cat. This high flow cat downpipe is specific to the B9.5 facelift platform which uses a V-band style connection at the turbocharger, making it a perfect fit for the 40 TFSI or 45 TFSI Hybrid models. 3.5″ diameter stainless steel piping with a high-flow catalytic converter is matched perfectly to a billet v-band flange, allowing for optimal flow as exhaust gases transition from the turbocharger to the rest of the exhaust system. Substantial power gains, improved exhaust flow and a more sporty sound are the main benefits from installing the CTS downpipe. Our friends at Boost Dynamic Tuning created the best Stage 2 file for this Simos 19.7 EA888.4 platform. CTS Turbo + BDT stage 2 combo is the best bang-for-the-buck performance upgrade for B9.5 40TFSI/45TFSI owners. Now available with end-user at-home tuning. Please see the link below for the compatible software tuning options: Boost Dynamic Tuning Stage 2 for Audi A4/A5 45TFSI Boost Dynamic Tuning Stage 2 for Audi Q5 45TFSI Product features

• Designed using the latest 3D prototyping technology for perfect fit into factory location
• High-flow catalytic converter
• Large 3.5″ stainless steel piping, billet stainless steel flanges
• Flanges are fully welded inside and out
• Welded stainless steel mounting bolts for easy installation (saves you a lot of time)
• New gasket and copper lock nuts are included, if you wish to renew the turbo gasket: 5Q0253115C
• Not recommended for crackle/aggressive overrun tunes
• Compatible with factory or aftermarket cat-back exhaust systems

To remove the CEL that will occur, proper tuning software must be used. CTS Turbo recommends Boost Dynamic Tuning. Fitment (for Borg Warner turbocharger 06N145702D):

• 2021-2025 Audi A4 2.0T 40TFSI/45TFSI (B9.5)
• 2021-2025 Audi A5 2.0T 40TFSI/45TFSI (B9.5)
• 2021-2025 Audi Q5 2.0T 40TFSI/45TFSI (B9.5)

INSTALLATION GUIDE BY BOOST DYNAMIC TUNING

This part also goes by the following cross reference.

Cross Reference Part Number:

Fits These Vehicles 5 applications

Q5

Make	Model	Engine	Years
AUDI	Q5 (B9)		2020–2023

A4

Make	Model	Engine	Years
AUDI	A4 (B9)		2024–2024
AUDI	A4 (B9/B9.5)		2020–2023

A5

Make	Model	Engine	Years
AUDI	A5 (B9)		2024–2024
AUDI	A5 (B9/B9.5)		2020–2023

Fitment data last updated: 2026-09-25

✓ Fits 5 vehicle applications Check vehicle fitment before ordering View fitment