_Slowbra_

it could be the o/r midpipe, but then that wouldnt have started right after he had it tuned, so it sounds like you are running rich. look for black soot/smoke in the catback to know for sure and check your timing like said earlier.running rich is gonna foul your sensors and waste gas but other than that i dont think it does much. idk for sure though, someone else will chime in.

Modular_Madness96

Did you remove the fuel pump fuse when installing the tune?It says right in the directions to do so or you could cause problems.

As for driving it no i wouldnt if youre smelling rawl gas fumes.

did you try returning the stock tune and see if it goes away?

_Slowbra_

modular ^^^ you have a very nice collection of cars. i envy you sir.

4literGasEater

Before you burned the new tune on your ecu you should have been asked to make a backup of your original ecu. go back and re write the original tune to the ecu and see if the problem resolves, if so you can take your car and get it dyno tuned