Mike,
I have a 1993 Corvette LT1 automatic trans.convert to which I have made the following changes:
1. Install high energy plug wires and platinum plugs.
2. K&N air filter installed.
3. Throttle body air foil installed.
4. Stock mufflers removed and 4 targa type mufflers installed. (Resonator left installed)
5. .258 rear end changed to .373
Somewhere along the way I developed a backfire from the tailpipes just as the transmission shifts from 1 to 2 under hard acceleration. No one at my chev dealership has an answer or a cure. Do you have any ideas?
Thank you in advance for your consideration.
Jim Ardito

You are getting air into the TPI system, I am not sure what the airfoil you installed accomplishes, but it sounds like it is in the right position to cause a problem as all the other modifications you have done don't do anything to allow a vacuum leak.

Mike