Do you guys notice a burning smell coming through that center (defogging?) vent mounted on top of the dash after you really get on the gas? It happens quite often for me. I've also posted recently about my windshield fogging up from the vent to the point where I'd be halfway through the 1/4 mile and have to let off the gas because I can't see ANYTHING. Dunno if this could be related, any help would be greatly appreciated. Thanks!

 

could be a hairline crack in your heater core...

for a WOT smell, there is a hot engine smell that occurs when you thrash on it..

 

bypass your heater core.

 

I know this is a long shot, but when I first got my car, one of the vaccum lines was not secured down, and whenever i hit it at WOT, the line would touch something and start melting...shot in the dark, but it's a quick fix.
good luck
-mj