I started out with an Intense PCM = it was ok
Then Rob Archer custom tuned my Intense PCM = much better
ZZP PCM, in the car for about 10 mintunes = horrible, got a refund.
A couple of custom tunes. = very good.

My son has an Overkill custom PCM in his 99GTP = highly recommended

IMO Overkill, is the only mail order PCM to consider.