Anyone Experience this??, Manual Tranny Shifting Problem Options

[Fastbird]

This is probably going to be for the forced induction guys more than anyone, but here's my issue:

I CANNOT hit a hard shift into 2nd at WOT in the car. Simply put, the tranny refuses to go into 2nd gear, and third gear offers quite a bit of resistance at high throttle inputs also. When driving easily however, it shifts fine into any gear I want it to.

Call me crazy but I've always had trouble shifting cable actuated manual transmission under heavy loads. What I think is happening is that my old/weak motor mounts are allowing enough movement in the motor that enough of a shift happens to throw off the sync of the cables to the shifter. What I'm trying to do is get some verification on this.

Thoughts? I must have tried 4-5 times last night on the way home from work to bang a high RPM WOT 1-2 shift and it wouldn't happen.