So w/ the 1.6's you have 622/627 lift. I run a similar 588 comp solid roller. Mine pulls until about 6400, I'm guessing with the hemi you should be pulling a few more RPMs. What are you shifting at? When it lays down are you higher up in the RPMs or is it coming on early? Do you have a fuel pressure gauge? I think that is what I'd be watching next pass.