dealer installed new egr and some baffle now my mileage is down to 11mpg from 15.3 regularly. Anyone experience this or tell me where that baffle is located

 

Could you tell us why the vehicle had to go to the dealer for repairs.

 

I took it in under warranty for "coking" the exhaust didn't have the authentic diesel smell. Now it smells like diesel, but I'm getting 11mpg as opposed to before 15.3 mpg! I installed a Banks Tuner and I don't want them to void my warranty! Where is this baffle located??? It must go. !!!!!!!