I've been having this problem for quite some time. My car (2004 toyota harrier) produces this "hangit" smell whenever I accelerate quickly (floored the acceleration pedal).
Send the car to a number of mechanics and a couple of them said that the problem is with the A/C. I tried turning off the A/C when I floored the car, and it didn't smell.
Have you encountered this problem before? And how much do you expect it'll cost for you to look/diagnose the problem?