Thanks for all the input, guys. At this point, I think I'm going to tune what I have and see where I'm at. I still need to bolt on a set of headers and get rid of these heavy manifolds. At only 340 inches, would good heads even do anything for me since it's not a race car, just a fun weekend cruiser? The X heads are fresh, so I'm reluctant to put money into them if the gain would be minimal.