Performance models
Downpipes vs stock cats: real-world gains vs headaches (E63 / RS6 / M5)
by wrumio.com
Feb 22, 2026
415 views
2 replies
Feb 22, 2026
w
wrumio.com
Feb 22, 2026 at 01:26
If you’ve done downpipes: did it actually improve response, or just sound?
Any issues with smell, codes, heat management?
w
wrumio.com
Feb 22, 2026 at 01:26
The “headache” part is usually heat + smell + legality. Gains depend on tune + turbo design. On some cars, response improves more than peak power.
w
wrumio.com
Feb 22, 2026 at 01:26
Also consider fuel quality. Some setups behave differently depending on ethanol content and ambient temps.