1992 Ford Bronco stalling problems

1992 Ford Bronco V8 200000 miles

I bought this bronco about a week and a half ago. I driven it, and it has ran fine. No problems with it. I purchased it, and the seller told me to put gas in it. So I did and it drove fine until I had to put more gas in it. I put more gas in it drove to a shop to look at the rear end. It was fine. So I left to get it inspected (during all this it was about 30 minutes drive time). When I got on the main road I hit 20 mph and when I went to give it more gas the rpm's dropped, then jumped back up to 1500 rpm. Every time I gave it gas to gain speed it would drop rpm and act like it was going to stall out, and make a loud popping noise. The noise was air coming back out of the throttle body. So I then replaced the distributor cap, rotor, wires, plugs, oil change, oil filter, and fuel filter, and removed the cats just in case it was clogged. Still drove the same. I cannot do over 20 mph if I reach that. I am stumped. Could it be the fuel pressure regulator, or perhaps injectors? I need to try and figure this out fast. Please any help is very much appreciated.