Well, from everything I've heard about the Purple Shaft cam, it seems like your root problem lies only in your rear gear and cam selection. My understanding is that cam offers so much duration that it really only offers a strong powerband above 3000-3500 rpms. That, combined with your high 2.94 gears, seem to me to be the only problems. The 292 purple shaft seems like a lot of cam for a 318, so I wouldn't be too surprised to hear that the thing doesn't really rip until higher RPMs. Maybe the .484 lift Purple Cam and/or lower gears would be a better choice for your combo?