Working on a '97 LT1 Camaro, 58mm TB, 1.7 rockers, Holley intake, no cam. Pulls like a homesick angel through 4K. After 4K, it begins to (for lack of a better term) "break up," like it's starving for fuel or hitting the rev limiter. WB looks good, about 12.8, so plenty of fuel. Not even close to the rev limiter. I added 2 degress of timing between 4K and 6K, above 60kPa, and that seemed to alleviate some of the problem, but the stutter is still there. Without KR data (for some reason the HPT scanner won't log it), I don't really want to throw more timing at it. Owner thinks that maybe the valve prelash is set too tight.

Any thoughts?