Hi, I searched/scanned the board yesterday trying to find a solution for my RS's surging problems. One thing I did find out quickly is that I am not alone in having this problem. My RS is a 92 Hertiage Edition Convertible, I have changed the following items:
Fuel Filter
Plugs
Wires
Cap & Rotor
Check some not all vaccum lines
And she still surges pretty bad, needle indicates that the RPMS toggle between 500-1250, pretty bad! I read that a couple members changed their fuel pumps and that solved the issue for them, others traced their surging to a bad vaccum line, another I think was a hole in the PVC line. Anything else? Oh my injectors are spraying nicely no sloppy dripping Could someone please give me more items to check, even throw out some ideas. She is going to be swapped to TPI soon because I have one and half TPI setups as my IROC has a new Super Ram and I picked up some TPI parts at a swap meet. However I would like more time before I tear into the swap and would really like to solve this problem. TIA!!!

 

Check your TPS, it was my surging problem, twice.

 

I had a problem with a vacuum leak that caused surging.Also about 600-1300 RPM.It would get better when it got warmer.Anyway, it was the throttle body leaking at the base.Found it by spraying carb/choke cleaner around seams until idle changed.
Bottom of my throttle body was not very flat.
I removed it and used a 1" thick block of aluminum with sandpaper wrapped around it to level it off.
Reinstalled it and all is well.
-Rich-

 

I replaced all my sensors but I think it was my MAP sensor or my O2 sensor that was causing it. That solved my problem...

 

EGR valve may be bad