No top end power, need help

Sounds like the secondaries may not even be opening. Sometimes the air blade gets stuck in the closed position and won't open even though you floored it. I found this on my GTX, as the engine coughed at WOT but ran great just under that.

Also, check to ensure that the gas pedal has enough travel to fully open the throttle. I found once that WOT couldn't engage the secondaries due to insufficient pedal travel.