I don't know anything about the de-tuning, for or against. I personally havd my clutch, flyweel, pressure place, and slave cylinder all replaced under warranty, and I found no decrease in power after the PCM upgrade. But just because the vec2 increases power doesn't imply anything about detuning. I've reprogramed a 2000 C5 among other vehicles, and I always dyno before and afterwards, and always reap rewards. Not to logical to assume that just because an aftermarket part increases power that DC de-tuned. If this were the case, then why do so many other vehicles have PCM modules or reprogramming availabe. The next illogical deduction from there would be to assume that all vehicles that gain any increase from a PCM upgrade must have been detuned. Just my .02.