When pressing the gas the car stalls and backfires

THE CHEAPEST SOLUTIONS IS A TUNE UP....

There are to many things that can cause the problem you have. Best thing we can do is get the DTC codes to understand better why your car is doing what it's doing.
The On Board Diagnostic (OBD) was designed on vehicles equipped with electronic fuel injection so you can generally retrieve the codes yourself. No need buying a scanner or running to any parts stores to check the engine light. This system is called obd1 and applies to most vehicles made before 1995 for domestics.

For GM domestic vehicles made before 1995, the diagnostic connector is located under the dash panel by the driver side. To get the check engine codes to flash in your dash panel, use a jumper wire or a paper clip and connect terminals A and B of the diagnostic connector. Turn your ignition key on with engine off and the codes should start to blink. All codes should start with code 12 which is one long flash followed by 2 short flashes. This code 12 means the diagnostic system is normal and will repeat itself continuously if there are no trouble codes. Otherwise, code 12 will flash 3 times before flashing the fault codes.

Counting the codes being flashed is almost quickest way to understand the Vehical's Engine Management and performance and most of the codes can be erased or cleared by disconnecting the battery negative terminal for 1 minute and reconnect. 
Just make sure to check your service manual in case you have electronic equipment such as radio or clock that needs reprogramming in which battery disconnection is not recommended. Finally after performing repairs on the culprit code, always go for a road test to confirm if the problem is fixed.

Good luck and here is a link with the OBD codes, let me know if you need more help. http://chevythunder.com/199295_lt1_trouble_codes.htm#Code 28