1993 Ford Mustang Backfires when cold

When I fire up the car and take off after warm up, the thing bogs. I floor the gas and it will sputter and do a weird backfire/thump from the front right section of the engine compartment. After that initial backfire, it will run perfectly until I turn it off. Even if I only turn it off to get gas, when I restart, the same thing happens. I am thinking maybe the smog pump?
It has all new temp sensors, oxygen sensors, air filter etc. HELP!