quick curt

i have a 98 ss with patriot stage 2,ls6 intake,slp long tubes,comp. cams 581/581-224 -224@114 the car only made 290 r.w.h.p. i have had the car at livernois motorsports and they told me the car was running on the low octane table at 21 degrees of timing and every time he tried to add timing it would take it right back out.no codes showing!then i took the car to speed inc. in schaumberg ill. they cant figure it out either so the tuner used ls1 edit to write over my low octane table with the high octane table at 27 degrees of timing , no change except now the car bucks a little. i use sunoco 94 and sunoco 100 unleaded 50/50 mixture. the car runs 13:10 on the motor and 11:34 on a 75 h.p. t.n.t. wet shot.