I'm about to pull my hair out over this any suggestions would be helpful. I have an 89 RS which has been converted from a 305 to 350. Basically everything is new with the exception of the throttle body. The motor is out of a 95 van the throttle body came with it. I have verified the injectors are 55# and have a chip form TBIChips.

I do not have a fuel pressure gauge but the pump is new. I cannot find a vacuum leak and have set base timing, tps, and IAC. One message board said to try a spark module for the 350 as they are different. This did nothing. I have run WINALDL and from what I can see everything looks good. The car when cold will start fine and idle high for a few minutes when the idle returns to normal it will start surging first slow and building on itself until the RPM drops to 400 and then the car dies. I can usually help the idle by applying some gas to smooth it out but it will start in again. Once it is warm the problem is less noticeable but still there.

A manual vacuum gauge shows the same as the map does. I have checked all the ground wires I can find and feel that everything is connected correctly. EGR is disconnected (which doesn't run at low idle anyway).

Could miss adjusted valves cause a vacuum problem that I don't see at high RPM? I adjusted them prior to installing the motor about a year ago, 0 lash + 3/4 turn. The car runs good at speed with plenty of power. I'm convinced it is a vacuum issue but cannot seem to put my finger on it.

Also my CE light quit working the other day. I have seen it come on once since so I believe there is a short. I tested the pin from the ECM with a led test light expecting to see codes there with pins A & B jumped but saw nothing. Not sure if it is a bad connection in the dash or a ECM problem.

Any thoughts?