My '91 N/A is throwing codes 12 and 18....throttle position sensor. Of course, I'm getting bad pulsing idle. My question is: Does this mean that the TPS is shot and needs replacing, or does it mean that the TPS just needs adjustment?

 

did you try checking resistance or ohms on the TPS

 

Not necessarily. Could be a short in the wire, bad connect at ECU or sensor...Grab an ohmmeter and check the sensor to see if it's bad. i dont know the S5 check procedure, but a search should come up with it.