[BOOSTED-SS-ELKY]

I had that problem with my 454, it turned that it need bigger squirters for the accelerator pump. And I also had the wrong plugs in the engine, and I had to adjust the linkage on the pump. Works good now.

^ Bingo

This is most likely being caused by a lean condition. When you floor the accelerator, there is not enough gas going into your engine and its falling on it's face.