[shorod]

If it was just the tailpipe at the rear of the vehicle, about the only thing I can think of back there that could create the no start would be the fuel pump and associated wiring. I suppose if they torched off the old tail pipe or welded the new one on they might have managed to damage the fuel pump wiring. Or just the work back there wiggling the old off and new on might have caused an already fatigued wire to finally break.

Do you have some throttle body cleaner or starting fluid that you could use to see if the engine will start and run if that's sprayed in the intake? Or can you hear the fuel pump run for a second or so when the key is turned to the Run position?

-Rod