BTCC A4

Will this make difference in power?
Should I just get a down pipe and not the Hi flow cat?
Or should I get both?
What kind of power gains will it give me with my brullen exhaust?

Par 5

you changed the cat to a free flowing one. Stock cats are typically stifling and you can get a bigger gain in hp by replacing it. Keep in mind that he was speaking generally, and not about the A4 specifically.

Zed 2.0

Hmm... I have to wonder about that, cuz ppl here get ~7% gains with a cat-back

Ash

...as far as the cat goes, a lot of people here say that it's not as restrictive as you think...if you can find a good high-flow cat that passes emissions, then go for it, otherwise I don't think you'll miss out on it too much.

Ash

Stang Guy

The Ford Mustang Cobra R&D team can vouch for that, take a look at all the problems they had with the 99 Cobra. They lost up to 30hp on their production models just because the exhaust from the cat back did not flow as well as pre-production models. They had to dimple the pipe slightly to provide clearance under/around the new IRS system, and it robbed them of power.

Also, you throw a cat-back system on a V8 and its not unusual to pick up 10-30hp gains. Edelbrock has dyno info showing such, and my ***-dyno confirmed this when I increased the diameter of my exhaust on my V8 Mustang. My $0.2. FWIW YOMV yadda yadda yadda.

Par 5

You're talking about high performance cars. He was talking about more "normal" cars like ours.