I have a 1989 rs 305 tbi 5spd. There are 2 wires with connectors by the t5. I know 1 is for reverse lights and I have it plugged into the connector. there is 1 more in the same wire loom with the same type connector but I can't find any place for it to go on the t5.Where does it go and what could it be for. I have speedo cable, is it possible that a 89 had a electronic speedo and someone replaced the t5 with a mechanical one. Any help would be appreciated.

 

Your car would have come with the electronic speedo, driven by a VSS in the transmission. Hard to say what might have happened to it since then.

The reverse lights wires are dk blue & dk green. The VSS wires are yellow & purple. What color wires do you have extra?

Nothing about "wc" has anything to do with that.

 

It definitely has a mechanical speedo cable connected to the t5. Speedometer does work, the dash must have been converted also.The connector not hooked up must be the original vss connector. Will it cause any problem with engine management if I leave it unplugged?

 

Probably....

That tends to affect the idle. The ECM is VERY confused about how fast the car is going, and does strange things.

 

The last year was '89 for Camaros with mechanical speedos. '85 for Firebirds.
Your profile info ('91 Camaro) threw me off for a brief moment too.

The back of the speedometer has an optical sensor type VSS which feeds cruise and the ECM.

Wire colours, and tracing where the wires go would be helpful to figure out your question.