2001 S10 Blazer Best way to test for clean Voltage from Alt

I have a 2001 S10 Blazer that I have been fighting a misfire for awhile. It is not bad enough to set a code but does disable the Torque converter lockup once and a while. I have replaced the entire ing system (distributor, cap & rotor, coil, wires, and plugs}. Cam retard is set at 0. Grounds have been checked. The last thing I replaced was the MAF and it actually helped the most but did not totally fix the problem. What is odd now that I am starting to use the A/C that the idle is rock steady with the AC on, with out the A/C on it has a random misfire at idle. Driving it with the A/C on, the misfire almost goes totally away. So I'm thinking that I have something going on with the Alt. like maybe some AC current hanging on the DC output of the alt. What/where is the best place to test for this and is some AC ok?

Without the A/C working: Is the miss present at idle only or in other rpm/load ranges as well?

Best testing point for ac-ripple is from b+ alternator output to alternator case ground.

Some ac-ripple is acceptable, the amount depends on alternator load/rpm...an often quoted number is maximum 300 mV at idle.

It is present at other RPM/Loads but much less when the A/C is on.

Thanks for the info on testing for AC on the DC from the Alt.