What's going on with my bronco?

Well, i just replaced the fuel filter on my 1994 ford bronco, and now couple times i drive somewhere, the check engine light flashes, and the truck's rpms drop, sputters, almost dies, but keeps going, and when i take my foot off the gas, it still applies gas, up to 1500 Rpm, not alot, but even when i push on the brakes, it still accelerates, but not when i come to a full stop. Several months ago, a buddy and i took off the exhaust pipe and muffler, to make it retain a more throaty roar, but i'm wondering if that could be the cause for the engine problem. But i believe it to be another problem., the idle air flow valve, hasn't been changed in awhile, and i believe that maybe the cause for the malfunctions, originally i thought it was the fuel filter, but ever since i've changed it, it's been acting the same or worse. What do you think?

I would suggest, based on what you've presented, that neither your "buddy" nor you have any inkling of things mechanical and seek out the service of a professional mechanic instead.

The exhaust can absolutely be a problem as that will effect your oxygen sensor readings.

Your throttle issues could be a sticky cable or throttle body shaft but could also be the throttle position sensor. There's also a chance that your idle speed control is leaking air and causing the idle to surge.

Inspecting the throttle body and cable is easy enough, a TPS and ISC will cost less than $150.00.

If you have your old exhaust put it back on with a Flowmaster if sound is a concern to you.

Check your fuel injectors, they might be open, when it should be closed, thats why you have 1500 rpm, and rpm can't go higher for lack of pressure

No matter what brand of car, you're supposed to shut the motor off immediately when the check engine light is flashing. Flashing check engine lights are the worst type. Have the car trucked to the dealer so they can read the fault code and fix the problem.