'96 LSi - Cylinder 3 Misfire

[dizzan]

Hi all... been a while since I last posted. Last I was here, I had just got one of the original PWR rad's installed, then some jack**s rear-ended me and totalled my '92 LS-L!

I finally found a new SVX recently, a 96 LSi, about 115k miles. It's been treating me well for the most part, but recently (2-3 months ago) there was a smallish exhaust leak right before the main catalytic, caused by the flange gasket deteriorating. I attempted to repair it but couldn't find the exact part (locally) at the time. It was better, but not perfect. Slowly, it's been getting worse again.

While getting ready to replace the gasket and associated pieces to get the exhaust sealed up, I started getting a check engine light. OBDII reader shows me P0303 - Cylinder 3 misfire. I found conflicting information on which is cylinder 3, so I checked the middle plug on both sides of the engine. Both are getting spark. The plugs were recently replaced with Bosch platinum 2's and are still almost brand new looking, though I swapped them out just to be on the safe side. Cleared codes, and P0303 came back again after letting the car idle for a few minutes.

The symptoms of what's happening are as follows:
- Motor shakes pretty bad below ~800rpm, but runs much smoother > 1000 and even > 2000.
- While driving, you can hear what sounds like misfiring especially at low rpm.
- There is a distinct and severe lack of power as opposed to when it was running correctly.

My question is, could the misfire be caused by the lack of compression due to the exhaust leak, or would you think there may be something else causing it?

I'm planning on repairing the exhaust in the next week or so once I get the parts needed. I hope that clears everything up, but in the mean time I was wondering if anyone had any suggestions on what else to check to narrow down the problem.

Thanks!
Dan