OK, I think somewhere earlier I made a post about this problem, but I think it might be worth mentioning again, or maybe saying it in a different way. Looking at the 60' times from a few posts up of 2.6x, I think this tells the whole story. irpq's dyno results arent' great, but IMO don't explain fully the very poor performance off the line. This is because the dyno is not done in first gear, and does not represent a launch scenario. It is a slow steady pull in one gear (4th).
Think about that 2.6x 60' time, I think I could run faster than that!
Seriously, my wife managed a 2.2x in her '01 z28 with a 2.73 rear end, and she had never been to the track before, and is no expert, believe me. When one of you guys with the slow cars gets to the track and posts measured 60' times to back up the iphone results, I think it will be clear where the issue is. I think it is mostly about the PCM limiting power from a standing start.
I know that the dyno results were goofy as well, but I don't think that explains the whole issue.
irpq11, can you repost your range of 60' times for your runs?