Roller Camshaft Rpm Range

i call jobs like these: death by 1000 cuts

tune is out just a little bit: wrong heat range of plugs, or gap; distributor is off a little, pick up clearance, ecu, advance rate/area; fuel is off a little, pump can't deliver at higher RPM, fuel line not adequate, filter is bobo; carb tune is off a little, needle/seat or jets

mechanical is out a little: springs aren't set up right, binding, aren't correct for the application; lifters going into pump up, floating the valves a little bit; carb linkage binding, not attaining full throttle; wrong intake or a severe port mismatch, pushrods too long/short or rockers adjusted incorrectly

and so on, and so forth.

check everything, but most importantly only change one thing at a time! just shotgunning parts at it is a terrible practice. while fixing it on a lucky guess is cool and all, doing the diagnostics and eliminating variables is more beneficial in the long run.

sounds like you're on the right track, you'll get it amigo!