Take the head off, rub a marker on the gasket surface and deck it on a flat surface with 220 grit in a figure-eight pattern, and get a thin head gasket from SBP. This raises the compression, thus power. Plus, like everyone here has said, match the manifolds to the jug, using the gaskets as a template. Taking the muffler apart and removing the stupid welded baffles and drilling a few more 5/16" holes in the inner core, near the bottom end help a bunch. I hacksawed off 2" too, and that helped a little. Enjoy the new ride!