[Ed Wright]

I doubt 16 volts would effect the performance of a carbureted engine.

My EFI LT1 did need leaned down when changing to 16 volts.
All I could figure was the injectors going fully open faster? More of their duty cycle is spent wide open?

I still have my 12 volt tunes. Just in case.

It does start up quicker, spins over faster, and likely has a hotter spark while the starter is also drawing current. Seems to cool back down faster on the return road, I'm assuming from the electric fans & electric water pump running faster? Those fans really spin now. :-)

I like 16 volts. Does it run quicker/faster on 16 volts than 12 if tuned correctly both ways? Nope.
And, I'm with Larry on the XM batteries & chargers.

And, I talked to the mfgrs of my electric water pump, and fuel pump. Both told me they were designed to run on 16 volts, since that is so common. MSD told me the same thing about their products, as did FAST. I have found no down side, except maybe battery weight.