I think that 16.5 is way too high. I have LED bulbs for basically everything except the gauges and never see above 14.5. Do you have another voltmeter to compare against? If you do take a reading right at the battery and see what you voltage is at a few different RPM ranges, (idle, 3K etc) a faulty R/R can cause the voltage to go high. After market meters can be finicky so it’s best to check with an external if you can.