Update: after much stuffing around, and purchase of a MDI clone, a subscription to tech connect (tech2win & SPS) I have been able to determine the ECM is bad, with no fuel pump signal to the regulator, immobiliser is off and all other units are operational (except for the airbag, it's getting replaced today), the New (used) ECM was programmed and has excepted the correct vin, but to finalise the installation, you have to do what GM call a 10 minute tdm (theft control module) to ECM relearn using the tech2win, (this allows the ECM to actuate the fuel system). only issue is the tech2win does what it's supposed to do, but requests tis2000 approval for the ok before starting the relearn, my version of techconnect doesn't show tis2web (tis2000), but it is supposed to accompany the tech2win software. I believe this is a common issue and I hope someone can provide me with s solution (emailed GM, waiting on response)
other alternative is to find a copy of TIS2000, as this will allow me to do it directly.
I have found a few "FREE" versions on the web, but they all are dodgy, or my virus protection block them, probably for good reason.