This problem all started a week ago when my girlfriend was driving it home from work and it started running rich to the point where it would stall out. I towed it home and replaced the coolant temp sensor, and it rand better but it would surge at idle. I found out the EGR valve was sticking so i took it apart and cleaned. That didn't fix the condition so i brought it to a shop and they said my lower intake manifold gasket was leaking or i had bad o-rings on the injectors. So i canged the intake manifold gasket and all the injector o-rings. That seemed to fix the issue for a while until my girlfriend took it about 2 miles from home and when she started it to leave it wouldn't rev above 2,000 rpms so she couldn't drive faster than 10 mph. I tested the fuel pressure regulator and changed the fuel filter and the oxygen sensor I cut out the catalytic converter because it sounded plugged up, that didn't fix anything. I've also tested the throttle position sensor, tested the MAP sensor, changed out the oxygen sensor, and the computer will not trip a code. Now I am at a loss, I've been told it could be a bad ECU but I don't wanna sink 100 dollars in the car on a hunch. Does anyone out there have any useful insight?

P.S. I know it sounds like mass air flow sensor but this vehicle is not equipped with one.