'94 Mustang-Various Issues

I have a 94 Ford Mustang SRS (If that matters) that idles too high (about 2kRPM) upon start up. If you try to accelerate the vehicle before it's gotten, uh, stable? I guess, the RPM's drop dramatically (500 or less) and has died in the middle of traffic before due to this. It also backfires, and has a really hard time accelerating when starting from a dead standstill. What could cause this?

I've tried nothing because every time I go to any mechanic they treat me like I'm an idiot and tell me that my brand new brakes and oil could be the problem.

First I'd look for a vacuum leak and proper operation of the Idle Air Control Valve. The IAC valve is located on the side of the intake plenum. A small tube from the air intake hose should branch off to this unit and it should be held on by 2 10mm bolts. It takes only a few minutes to take off. Sometimes they get dirty and they stick, causing high or low idles and stalling. Cleaning them may help. Replacing it might be necessary and Autozone should have a Duralast replacement around $80.

If the IAC valve is okay, then look and listen for a vacuum leak. Check all of the hoses for cracks.

While you're at it check your MAF sensor. It is in the intake tube just after the air filter. Clean it off with CRC MAF Cleaner. Gunk can build up on it giving the computer invalid information.