my mods are...high compression block, xp cam, springs, speed daddy headers, gen 5, meth injection, northstar, 3.29 gears, and 3.1 pulley...problem is im getting bursts of knock at shift...itll hit 9 and drift down to zero but half the time it wont do it at all. took the timing down to 13 and ran the larger meth nozzle with very little difference. what could be causing this?