Originally Posted by Jordo!

I don't see how... you can't tune exhaust pulses with the ECU (well, you sort of could if we had control over VVEL...)

Anyway, just got test pipes on, and yes, it hisses a bit.

My buddy who did the install thinks it might be due to the fact the pipes are single walled, and that's just how they vibrate.

Note the big weights on the either bank of the exhaust around the Y-pipe -- this motor just has a lot of weird resonances to work around.

How long before you know for certain you're in the clear for getting a CEL? I've not driven too much yet, but have gone through multiple "trips".