Rev limiter problem after headswap

96GT is giving us fits with what seems like rev limit in the 4500rpm range after our headswap. Idles smooth as silk, smooth in normal driving. No codes thrown, but, with heavy accel or WOT only runs up to mid 4's and starts to shutdown like rev limit or los/limp mode. Smooth milder acceleration will pass the mid 4's on rpm. All sensors check ok, looking for ideas as to where to look next. Should we have the stock PCM reflashed? Stock cams with 24LB injectors and calibrated MAF. Hoping somebody can give us a clue.

In case you're interested

Our problem turned out not to be Rev limiter but instead weak coil packs. They were purchased new on Ebay, however, must have been factory seconds or improperly marked for this application, because when we changed them out for motorsports coil packs the spark was 10 times hotter and our stumble in closed loop or WOT disappeared. Shopping EBay for new/old stock or used parts didn't help keep our project costs down when we had to deal with problems created by those parts. We learned a good lesson.