WHen the A/C is on Recirculation and you floor it to pass or accelerate about 5 seconds later the cab smells like exhaust? Anyone have this problem or know what it could be? I have an 07 Aspen 4.7 with 57K miles on it......It doesn't do this if the A/C is set on fresh or outside air only on Recirc.....

 

Have the exhaust manifold gasket checked - there is probably a small leak.

 

I did some looking under the hood and there is no exhaust manifold leaking? I'm stumped?