Engine Question, dead til 3000RPM, ideas???

[chevy2racr]

ok, dad and have been workin with an 85 camaro all summer and we've fixed some quirks but theres one thing thats got us puzzeled. it a 355 with a Holley 750 Vac. 2ndaries. covette LT1 hydrolic lifter cam, headers, yada yada yada. has a MSD Digital 6 ignition. msd distrib..... and so on,well if you put a timing light on it(have a MSD light that reads as a tack as well) it never stays still it will be idoling and it willsay500RPM to 2000 RPMwithout any change in ga and it sounds like its idoling fairly steady, little rough, but nothing TERRIBLE. and according to that timgin light its timed somehere around 35 advanced, starts hard, but if we turn it so it should be timed closer to 20 on the road it pops back through the carb and runs like sh*t. so turn it back to where it was and the main problem still remains, if you lay into it it is slugish and jerky til it hits about 3000RPM and then it kicks ur a$$ back into the seat like none other. dad had te idea we needed a differnt dist. gear with the cam. ? anyone have anyideas??
anything may help.. thanks
Bryce