Help my car sucks SN95 GT

[Robert_5_liter]

Got Heads on and the car pulls good but not well after 5000 my scanmaster says my timing is pulled back to 24 degrees from 36 degrees this car keeps pulling the timing out it always has and my freinds 95 cobra is doing the almost the same with the timing is there something else i should know about with the computer. I tossed the chip it was junk after the car was modded but everybody says these cars had a not so performance minded computer.