Very rough idle. New plugs and wires. When I pull either of the 2 plug wires for the right side of the engine, hardly any change in performance. The plugs and wires are good. Is it possible the timing belt jumped a couple teeth on the right side sprocket? Why would both cylinders be unresponsive like that?

Did a compression test, both sides read 150. Stethoscope tick on all the injectors. Every wire getting a spark. Can't figure this one out.

Burnt valves?

Do a vacuum test...

I had this on my '96 GT a few months ago, and we eventually got to the bottom of it. It was the fuel pump dying.

The fuel pump was only pushing enough pressure to feed the 2 cylinders nearest the pump. The other 2 weren't working, and fouling the spark plugs.

We also had the air flow meter go on us at the same time, so it was bloody hard to untangle all the symptoms... we had a very sick car for a while.

So, new fuel pump and it's roaring along again.

Just had this happen to my Eagle Talon Turbo. It turned out that the Cam Location Sensor went bad. If there is no spark at all to those 2 cyl. it could be a crank or cam location sensor. Check the trouble codes to begin with. Bring to shop if you can't check the codes yourself.