Electrical Bucking under load - no starting or idle issues - Maybe electrical?

Thanks! It hasn't been driven all that much in the past couple years. It had been in storage for a bit while I was deployed and was stored in my garage. Just started and run every couple of weeks, so that might explain the dizzy/cap/rotor still looking good. The issues started before that though. I'm gonna take a closer look at the plug wires and coil over this weekend to see if there are any issues that can't be seen.

UPDATE: I have (I think) overcome! Even though the TFI tested good and I didn't find any visible issues with the coil, plugs, wires, etc, something was definitely affecting the spark.

Since I was at my wits end I did the only thing I had not yet done. I swapped out the distributor (and TFI). Low and behold, it worked! No more bucking under load, even with accessories running! Idle is great, and everything is good in the world (for now).

I appreciate all the helpful responses and suggestions. It definitely helped me narrow my focus and confirm a few things. I'm still not sure if it was the pip sensor or TFI, but whatever it was, hopefully it's fixed for good. Fingers crossed!

In the wise words of the Drive-by Truckers..."keep dropping the hammer and grinding the gears"!