I posted something similar (not the same) in the transmission area. Just want to ensure my V6 colleagues are aware of this issue.

The VSS for some T5's (GM Codes: D8G and D8M) are discontinued. It also appears that some or all aftermarket vendors have also discontinued that particular VSS. A lot of vendors say they have the correct VSS, but it is for the automatic not manual transmission.

After a long search, including phone calls to vendors, I found the compatible VSS (Standard Motor Parts #SC40) on Ebay. For a while, I was planning to go to the bone yard checking out certain year Caprices, Camaros, & Firebirds that have the same VSS. Luckily, I got the last one from one Ebay vendor.

However, I found 3 other Ebay vendors who still have the compatible VSS. If interested, just do an Ebay search for "Standard SC40."

 

P.S. Don't be dumb like me. Drain the transmission fluid before removing the VSS. If you don't, I can verify that a shower of fluid in your face is not pleasant. Not to mention embarrassing.

 

Had intermittent SES light, but could not get a code. Finally, left engine running when SES light was on and got a code 24. So I figured the VSS was going bad. Started searching for a new VSS. After car would only rough idle 500-800 rpm or 3,000 rpm, no in between, I finally found a replacement VSS.

After installing VSS, car runs fine. You are right, that when sensors go bad, the symptoms can vary resulting in some screwy, even baffling, behavior.