92 Chevy Lumina 3.1 Multi Port

When the car is started, it idles very high. I can't tell you what the RPMs are
because it doesn't have that gage on it for whatever reason, but I can
definitely hear that it's no where the idle should be. If I put it into reverse, it
immediately stalls; if I put it into drive, it boggs down a bit and tries to stall,
but if I keep my foot on the gas a bit, it won't. When it is moving, I have to
keep the gas just barely on, not pushing the car more than 10mph or it will
bog out real bad. If I try to give it more gas, it absolutely won't go any faster
and acts like I haven't given it any more gas than before. It puts real badly
and will stall out when coming to a stop. Sometimes, I can keep it running if I
keep the gas pedal pushed down a little bit, but that doesn't usually work.
Now... this car only acts like this when the check engine light is on. When it's
not on, the car runs just like it should, but it still idles high. Sometimes the
light comes on and the car acts stupid, while other times, it acts as if there's
nothing wrong with it. I've replaced the throttle position sensor to no avail. I
was told that it is probably the Mass Air Flow Sensor but I can't seem to find
the thing on the engine. I'm wondering if the vehicle even has one, although I
read that any vehicle that has a fuel injection does. I thought that it may be
the fuel pump that's going out but I was also told by a licensed mechanic that
those rarely go out and that it is almost always something else. So I am
stuck now and not sure where to go with this next.