Is the cam timing the problem, or something else?

How far can you "wind" it? Does it seem to perform better on top end? If so that is normally RETARDED cam timing rather than ADVANCED, which tends to help lower RPM

If you changed the cam drive, IE sprockets and gears, that is replaced them, with same physical cam, that could do it. What they are talking about is MACHINING TOLERANCES in the cam/ drive. You can check cam "degree" if you are careful without removing the cam. You likely will have to remove intake, but you might pull it off by not doing so. You have to think and think outside the box and get creative. Maybe buy / find some junk pushrods and convert them into extra long so that you can bring them up /out far enough to "get ahold of them" with a dial indicator. This of course only works if you know for sure just exactly what cam you have in there and access to the "cam card" (cam specs

HOW ABOUT TIMING?? Where do you have timing set and

CAVEAT:: Some timing marks are not accurate (use a piston stop) AND SOME TIMING LIGHTS are not accurate with MSD ignition. This is a well known fact. Find yourself an old timing light that is NOT a "delay" or "dial up" light

I assume?? (maybe I should not?) that you have checked jetting/ plug readings, and DOES THE THROTTLE open all the way?