[abs]

In general, a bad MAF (mass air flow) sensor can cause severe engine performance problems when they go bad. Thing like low power and bucking/kicking/stalling. On some engines (not sure about Northstar), if you disconnect the MAF from the computer, the engine will fall back to a default limp mode which is sufficient to test and get an idea if the real culprit could be the MAF. I would try that and see what happens.

Andrew