No attempt at being smug nor condescending here. We never know to what/whom we might be replying, and have no idea of their level of experience or expertise. I only wanted to be certain you understood the function of the device so we can proceed with the diagnosis and repair. Incidentally, on GM vehicles, it is also known as an "IAC" (Idle Air Control, because that's what it does).
If the "35" is repeating after having replaced the IAC, there is likely a problem with the connection between the IAC and ECM, or a problem with the output transistors in the ECM itself. The latter can be a lot harder to repair, and ECM replacement would likely be easier. Unfortunately, you might need to access the ECM and expose its connectors to be able to check the continuity between the ISC connector and ECM connector.
A somewhat easier way to determine if the IAC is getting pulses from the ECM is to remove it from the throttle body, place it securely in a plastic bag with the electrical connector attached (in a bag so you don't lose the pintle and spring), place a jumper in the ALDL connector A and B terminals, and turn on the ignition without starting the engine. If the IAC coils are getting pulses from the ECM, the pintle and spring should extend (and possibly all the way until it falls apart, which is why it's in a plastic bag). If it doesn't move, there may be an ECM or wiring problem.
This will only work on older, non-OBD-II engine controls, and I believe your '94 would be included. If the ALDL connector under the dash has terminals in the A and B positions, it should work:
There is also the possibility of a general poor connection issue with the ECM, which might also explain the rich and lean exhaust sensor codes.