Are you sure the gauge is working correctly? It may be reading high. Batteries will take 15 volts OK, but that's about it. That's why 14.9 for a short time is not a worry. My "guess" is that 14.9 constant is OK too. This is assuming that the wiring is up to par. Hopefully an expert on the subject will chime in so we both know for sure.

I'd try yet another brand of voltage regulator. I know that two different regulators I ran were something like three tenths off from each other. One was from Autozone, the other from CarQuest.