Correct voltage and regulator question

[Cap'n Carageous]

My voltage at 1500 RPM ranges from 13.31 to 13.39 with no major electric consumers on (A/C etc.). Is that sufficient? Also, even though voltage is steady, can a regulator or alternator diode cause electrical problems(gremlins). I read a lot in a search but most of what I saw was not conclusive.