I already know I have an exhaust manifold leak, but I have a rattling noise that I cant seem to pinpoint. It happens under light accel when it gets up to about 2-2.5k rpm, at about 3k it seems to go away or the motor noise is drowning it out. It sounds like a heat shield rattling or marbles in a can which seems to be consistent with pinging from what ive read. The car still seems to have plenty of power. I always 93 octane, I did replace the plugs a couple months ago with ac-delco iridium pre-gapped at .60 so I really don't think its the plugs. I do have a zzp pcm that I have also had in for a couple months as well. I'm thinking about swapping my original pcm back in to see if maybe the timing is off ? I heard rumors that the zzp pcm is not the greatest especially in Bonnevilles. Other than that could an exhaust manifold leak cause pinging ? Thanks

Best way to find out is to put the front end up on ramps, have someone get underneath and someone play on the throttle. Surely you could find the rattle in no time with someone underneath.

The problem you are describing is common to 2000-2003 SSEi. It is the Front flexible exhaust pipe. The parts you need to replace to fix this are:

Pipe- GM part # 10371540 retail 369.00
Gasket- GM part # 15286606 retail 26.49
Gasket- GM part # 3544534

Labor with proper tools is under 2 hours. You may be able to find alternate OEM parts for less. Most dealers will have to special order in these parts.

I forgot to mention it only happens under load, not in park or N.

I have a similar rattle and I am pretty sure it is coming from inside the cat. Since it is not an issue (other than the rattle) I have not changed it.

I had the problem, and had the dealer fix it (ouch).

That is unfortunately why I know the part numbers and cost, fund the invoice from the dealer. Work was done in 2007. No repeat of the problem after the parts were replaced.

Well if thats all it is then thanks guys. I was a bit concerned but since In didn't have a lack of power or any other symptom I wasn't really sure.