Check with your local auto parts stores to see if they have a smoke machine you can rent or borrow. That will let you force white smoke through a vacuum hose at 2 psi. Then you watch to see where it comes out. Intake manifold side gaskets are a common source on GM V-type engines but coolant leaks are more common.
The crankshaft sensor will cause a stalling or no-start problem. Most of the symptoms you mentioned could be attributed to a vacuum leak. Any "unmetered" air that gets in without going through the mass airflow sensor will result in unburned oxygen in the exhaust where it will be detected by the oxygen sensors. That will direct the Engine Computer to add more fuel to the mixture. No matter how much fuel is added, there will always be that extra air.
The same thing can happen from an exhaust leak ahead of the catalytic converter. Between the pulses of exhaust gas, the momentum creates pulses of vacuum that draws air in through the leak. That air gets detected as a lean condition on one side of the engine.
Friday, February 11th, 2011 AT 1:08 AM