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.
I took a quick look at the secondaries and they move freely. this doesnt tell me though if they moove while the engine is running. another thing I will check this weekend. Guessing I can just have the car in park witht the air cleaner off and open the throttle and I should see the secondaries open up (hopefully)?
