I'm pretty sure I have an exhaust leak. I can hear it when the engine is running, and it gets more intense as I give it more gas. I can also smell gas/fumes a pretty decent amount.

I looked last night and I *think* I felt some air coming out where the header connects to the head. Took a couple pictures. See what you guys think. Each pipe on the header has kind of an indentation so the gasket is necessarily pushed in a little at each hole, but this last one (closest to the firewall) looks a little too out of shape. You can also see what looks to be some material from the gasket torn and sticking out toward the firewall.

 

Check and make sure the bolts are tight. If they are replace it?

 

Not uncommon at all especially at the centre cylinders. It certainly looks like there's a problem judging by the picture.
I had tried several makes of header gaskets; Fel-Pro, Mr. Gasket, even Percy's carbon fibre version and they all failed eventually. It doesn't help that I have Hedman's economy level header with the less than thick flange.
It wasn't until I made the move to a Remflex header gasket that my sealing problems were solved. Highly recommended.

 

Interesting ..hadnt heard of them before ....

http://catalog.remflex.com/CHEVROLET...ket_p/2004.htm

 

Those are the ones (1.5" round port). Worth every penny.
Summit has them for 28 bucks.

http://www.summitracing.com/int/part...2004/overview/