Brian, you mentioned slaving the elevators to the throttle. Check one thing before you do anything else and that is retract the landing gear and then check to make sure that there is no slave mix that is active only when the gear is retracted. It is highly unlikely that this is the case but it only takes a minute to rule that possibility out.

One other thing to try is rolling inverted and check to see if it still pitches skyward under power.
If it does then as you said check the cg. If not then go back again to triple check the decalage and pushrod mechanics.

Good luck,
Ross