Ford Repair: 1997 T-bird 3.8L poor acceleration and gas mileage., throttle position sensor, air control valve

Question
The car starts fine and idles relatively well. It will accelerate smoothly if you barely push the gas if you give it a lot of gas like if your trying to pull out quickly the car bogs and spits and sputters. I even thought I smelt a sulfur smell like the cat might be clogged. Once going the car will coast at normal speeds I've had it up to 80mph no problem. If you get into it it will kick down and the RPMS will shoot up like it should however it just bogs once again spits and sputters. I stopped the car at a gas station cut it off went inside came out restarted car. It ran great it would accelerat quickly at any speed and had lots of power. I just cleaned the IAC (Idle Air Control) valve. I'm guessing that this is a sensor problem can you point me in the right direction.
BTW the Check engine light is not coming on. The car has been getting terrible gas mileage.

Answer
Replace the fuel filter to start with.Having the fuel pressure tested couldn't hurt.There is a way to adjust the throttle position sensor with an ohm meter.You can find instructions in most of the repair manuals found in you're local parts store.Also,have the catalytic converters tested at you're local muffler shop.Does it seem like the transmission is slipping.