New charging problem

Are you using one of the big capacitors on your stereo system power feed? If so try disconnecting it and see what happens. A capacitor stores voltage and it's possible it's storing excess voltage causing the high reading.

BTW: If you use the internally regulated alternator the battery voltage will probably drop because of the voltage drop from the alt. to the battery. It'll defeat your mod you did where you ran a sense wire right to the battery.