The VR will make you happy.
Tstat change, no problemo...
On the MAF change. Your MAF is well up to the task of metering the air. I have not seen anyone post anything positive about the Granatelli MAF. Perhaps this thread will bring them out or a vendor who handles them will pop on and give us a better idea of what to expect, but, the only posts I have seen here and on ohter forums for C5 are that the car didn't gain power with it. Some lost a little. One guy tried it on many different C5's with no luck.
RG