A/C vibration

Hi folks, curious if anyone's experienced a similar issue to mine.

'98 with a stroker, AX-15, NP231, and tons of little mods. '99+ intake manifold upgrade, new PS pump, 136A alt, rubber Brown Dog motor mounts, relatively recent trans mount, etc etc.

I get a strange vibration when the A/C is on. I only notice it at idle but for all I know it's present throughout the rev range. It's enough to feel through the steering wheel and vibrate the mirrors. It isn't the electric fan, because I can pull the temp sensor to kick that over and it doesn't cause the vibration. Yet, looking at the fan belt I don't see any odd movement with the A/C operating. I can even put my hand on the compressor and it seems to feel normal. What gives? Could there be some internal balance issue that the A/C is making worse?

The only recent work that would have changed anything is an adjustment to the exhaust because I have a custom setup that, for a while, touched the bell housing of the trans and I didn't care for that. Now it has all the right clearances (as far as I can tell).

Suspects? Advice?

I experience the same vibrations when my AC is on and really only notice it while sitting at a light or stopped when the AC and engine running. Also seems to be more noticeable if the AW4 is in Drive w/my foot on the brake. I also have Brown Dog MM and a relatively new transmission mount. I noticed it a LOT more when I installed the Brown Dogs... but I also value my radiator not being cut up by my mechanical fan and I don't like replacing my MM's every 2 or so years. If there is something that's wrong and can be fixed I'd be interested to know as well.

Yeah the motor mounts are the obvious culprit for being stiffer than stock, except I've had them in for more than 10,000 miles and not noticed this vibration before. It is better or worse sometimes but occasionally bad enough to be audible, which is really annoying.