I ran a 12.53 @ 113 in Boise. Track elevation is 2700 Ft, corrected on that run I would venture to say was probably 4,000 Ft or better. That was with a slipping clutch (slightly).
Mods were - Open Air Cleaner Lid w/ K&N - Haibeck Chip - Watson Headers - Flowmaster Cat-Back Exhaust. That's it. Good burnout with 26 lbs of air in the tires (GS-D3's), I had a 1.92 60' time and I believe there was another .10th in it had the clutch been good. I fixed the clutch (Autozone), added a Fidanza Aluminum Flywheel and went back out. Popped a half-shaft u-joint on the the first pass at the starting line. Got that repaired, new half-shaft and all 4 u-joints. Back out again, but I had bought another ZR-1 so I didn't want to flog the car. No burnout, no air reduction in the tires, the car ran a 13.00 @ 113. The headers have now been removed to sell the car.
I think with 4:10's and Injector and Plenum work that 12.53 would have become a very low 12 or even a high 11. Remember this in Boise. Corrected for altitude it would/could have been 12.12 @ 117 (using NHRA Factors for S Stock and Stock). That's stout guys.