1989 Chevy Celebrity idles too high/sputters

Hi, I have been trying to fix my 89' Chevy Celebrity Wagon for a couple months now. I really dont know too much about cars but I dont have any money to give to a mechanic, so I was wondering if you could give me some advice. When it first broke down it started to sputter like it was out of gas (which it wasn't) and it would not start again. After towing it home I tested the fuel pressure, and it was low, so I thought we had a definate fuel delivery problem. I changed the fuel pump, and the pressure went back to normal but the car still wouldn't drive. (I did get it about a quarter mile down the road before it broke down again, but it was still sputtering) It now has a new throttle body positioning sensor, idle air control valve and fuel pump and it is running but it wont go over 35 mph, and it sputters/idles to high. I had a mechanic come out and hook it up to a scanner and he said that he couldn't get into the ECM to see if it was working or not. The same day I had bought a fuel pump relay and an oil pressure switch but he said that it couldn't be either of those causing the problem. I did remove the ECM and play with the wires/ hooked it back up again but to no avail. The pins all look good, and I called GM to make sure it is the correct ECM for that car, and it is. I really don't know what else to try. The mechanic that came out said he thought only three of the injectors were firing, I guess he cut a wire or a set of wires or something (to reset the injectors?) And then taped it back up. Doesn't sound like a great idea to me but he said all 6 were firing after. I really dont have any more money to put into this car but I cant sell it and I need something to get to work in (so I can fix it. Lol) so I was wondering if I should really try the ECM?