PatrickBateman

Bought some Top-speed (ebay) high flow cat headers for my 997.2 (105K miles) but don't want to do a tune- is there any reliability concern? As I understand it, the freer flowing headers may differ from what the ECU is looking for, and I don't want any issues that stem from altering air/fuel ratios from factory.

Is this an issue or are these cars happy to account for differences such as these without trading off reliability?

Frank 993 C4S

No issue. I have custom heeders and a stock ECU.

PatrickBateman

High flow?

EVOMMM

Frank who made them I need a set for my turbo S and 996

Chris M.

You may get a CEL and if you’re in an area with emissions testing you might have an issue passing. The @Softronic tune gets rid of the CEL, other brands may as well.

Petza914

If 200 cell cats, you'll be fine. If 100 cell cats, you'll get a cel.

Chris M.

Mine are Topspeed 200s (different from TopGear) and I had a CEL.

Frank 993 C4S

Custom M+M system sold by FVD in Germany. No cats. Not appropriate for a street car application IMHO.

Petza914

Maybe the .2s are more sensitive than the.1s. I've never had a cat CEL with my Fabspeed 200 cell cats, but they also use expensive HJS cats in their systems...no idea what Topspeed uses.

Did you try an O2 spacer or did you remove them?

Chris M.

Softronic tune took care of the CEL

Busta Rib

I installed Top Speed 200-cell headers on my GTS and got a CEL. Erased it with a custom GIAC tune. I do not recommend Top Speed headers because it seems the quality of the cats is poor, although they do sound good. I've read higher-quality headers from more established brands shouldn't throw a CEL but I don't have direct experience.