kimoses

As the title says, thats my car. I have two problems and need some help. My car loses voltage, that is monitored through a vafc, and drops from approx. 14.4 volts down to approx. 12.8. It only happens when it is warm. Started when the motor was put in last august??, and the alternator was replaced along with all of the ground wires being checked. My greddy turbo timer fried in the car after the engine was installed. Cannot figure out what the problem is, seeking help.

Also, I have a p28 with a diff. board that I use right now. when I put a stock p30 ecu on it, after a few minutes the car loses a lot of its power, but no check engine light. My buddy whose a mechanic told me it was my knock sensor, but wanted to get others opinion.

Thanks everyone.