I just recently did a t-5 swap into my GTA.. And ever since, as soon as it gets to operating temp while driving and push the clutch in it stalls, no matter what speed. I do not have a speedo sensor right now, trying to locate one. I've retuned with a manual tune, changed the tb, iac, tps, maf. The only code that i get is the Vss, which is due to the no speedo.
After the 4th or 5th restart, the car finally stays running normally, under any driving condition.

What would cause the stall in the first place? Shouldn't the ecm stall saver stop it from droping dead?

 

If the IAC is clean, lubricated, and functioning, it should respond to the ECM and prevent stalls. If your conversion ito T-5 is from an automatic, the programming is different, and the stall saver does not remove IAC counts with a manual as it does with an auto. It is intended to act as an electronic version of a dashpot for the manuals.