i'm working on a 94 mazda 626, 4cyl 5spd (not mine), and it recently developed a problem in which it smells like its running VERY rich, and, if its willing to start, it'll idle normally, and if you creep into the throttle you can rev up to about 3500 RPM max, any throttle beyond that point and it just dies out, regardless of RPM. i can barely make it limp around the neighborhood, and anything beyond that is hopeless.
after studying it and not being able to find a diagnostic computer for it, logic pointed toward a MAF sensor, so i bought one, installed it, and got the exact same results. i put the original sensor back in the car, and no change. next, i looked up how to manually pull codes using the flashing CEL without an additional computer. i got a code 16, which is for the EGR valve's sensor. the owner reports its been throwing that code for a long time, though the CEL is not coming on for it, or at all. that was the only code i got. from there, the only other thing i could think of was the TPS, so i looked up how to test it, and in the same article it said two contradicting things, so i followed the general practices listed first in the article, and used an ohm-meter to verify that it had a smooth change is resistance as the throttle is opened and closed, so that appears normal. and since it hasn't been removed or messed with, it appears not to be the problem.
where would you guys suggest going from here to solve this problem and get my friend back on the road?

 

oh, and the new MAF sensor i tried was NOT a cardone, so i expect it to be good. if it was from cardone, i would have expected the replacement to be bad, but as it is, i doubt its the problem