2-3 Shift flare up in a 904...

Hello,
I have a question on why my 904 flares up about 700-800 RPM when I shift at WOT. Here's the combo: Motor 511HP-340, 5,000 Stall Converter,
904 Trans with reverse manual VB (turbo action), all MP clutches and bands, Low gear set, 5.0 lever, and deep pan. I have a trans oil temp gauge in the car as well and even on the street with the 8-inch converter it hardly breaks 140 degrees, not enough heat? At normal driving it feels fine, but then again I have a 5,000 Stall conv. and the stall kind of hides the shift. I am not sure what other info you need to make a diagnosis. There is only 500 miles on the complete rebuild and it has done this from the begining. All clearences where set according to the turbo action instruction manual. The 1-2 shift will snap you head off...
Any Help???
Thanks,
Jeff