Replaced Alternator, now AFR's are lean...
 

I had my LS1 RX7 retuned a few weeks ago and we had a low voltage issue.

HPTuners wouldn't flash the PCM so we put a jumpbox on the battery. It flashed the PCM and my WOT AFR was 13.0

Yesterday my Alternator died, so I replaced it and now my WOT AFR is 14.0-14.3

Just wondering if this would normally happen due to voltage issues or something else happened during the meantime.

Does it cycle from 14's at all? Just wondering if your sensor crapped out and is at its default max setting.

Yes.

The lowest it will drop to is 14.0 though. AEM UEGO or EUGO, however its spelled.

Well my old UEGO, would stay in the 14's when the sensor died. I spent hours trying to fix my tune the first time it happened. Then I came to the realization, that my air fuel wouldn't change after adding any fuel.

Mine only has maybe 6-800 miles on it.

6-800 miles really doesn't matter. It all depends on the fuel you use. I could only get a couple hundred miles...if that out of mine. This was due to using leaded fuel

I had a brand new sensor fail within 2 months, age is irrelevant..

Heres a trick that sometimes works..

Remove your Wideband sensor, get a mapgas or propane torch and heat the end of the sensor until it is glowing hot, sometimes this will burn off the crap that is causing the fault, worth a shot..and if it works you saved yourself $80 on a new sensor.

THIS^^^

Have you tried to recalibrate the sensor in open air?

Drove the car last night and today, my AFR is getting closer and closer to my 13.0

Sometimes even held a 13.0

Its running alot better the more I drive it.