Engine running rough!

Okay, the car is a 95 2.3 Quad 4. I changed the plugs and even tried a coil, but to no avail the engine still runs rough. It will also make a loud knocking noise when I put it into reverse sometimes (which goes away when I hit the accelerator). If I put the car in neutral the engine smooths out a buit but I can still feel it surging slightly. There is some popping coming from the exhaust when it revs up. The vacuum lines are dry rotted, but I don't see any large, obvious holes. Also, when I took the vacuum line off of the fuel regulator the engine seemed to run slightly smoother. I also put a can off Gum-Out injector cleaner ointo the tank yesturday, but so far I have seen no improvement. The SES light is not on.

From the symptoms you described, here's a few things to try:

Clean your throttle body with throttle body cleaner
Clean your idle air control motor with throttle body cleaner
Clean your EGR valve

Your cat converter may be blocked (most possible)