Guys I can sometimes smell exhaust in my truck with the AC on Norm while it is regening. How can I tell if the exhaust is leaky or if the downpipe is cracked?

I can drive real slow and still smell it so it's not like I'm stopped and the smell is creeping up from the back. I can even stop while it's regening, set the brake and pop the hood and smell exhaust under the hood. What could be leaking?

 

Here is a TSB on it: Exhaust leak in engine compartment:
Some trucks may have an exhaust odor inside or exhaust smoke may be visible around the front. This could be caused by a leak at the turbo outlet from a misaligned downpipe. Verification requires disconnecting the turbo oil supply tubes (replace the banjo sealing washers, W302474) and removing the turbo heat shield to inspect. If the leak is at the turbo outlet, the downpipe will need to be repositioned to seal correctly, with a new downpipe to turbo gasket (7C3Z-6L612-B) and v-band clamp (7C3Z-5A231-AC), and new nuts for the downpipe to catalytic converter flange (W711407-S900). If properly installed, the downpipe will be 11/16" +/- 1/8" from the frame rail. TSB 07-7-7

 

Thanks. I'll mention this to the dealer.