4th gear stutter

Alright im going to try and explain this the best I can, so bare with me. When im in 4th gear full boost WOT the car will stutter once or twice, the feeling is like when the car is about to stall but it only does it for a quick second and it really is only in 4th gear. Any suggestions? Its a 98 GST I have a boost controller on it set to 15 - 15.5ish. I also have read the Car Sputter thread above and have checked to see if it was the plugs wires and MAF and it is none of those and I replaced the plugs with Bosch Golds gapped at .030 even though they should be at .028

start by gapping your plugs right...