Big electrical loads, grounding kit?
 

1986.5 na 5 speed. Had this problem since i had the car and just wondering if someone has or dealt with this similar issue. Every electrical load is "big". To attempt to explain, if i have my turn signal on the gauge is going from 14 to almost 12 with each flash. headlights, blower motor, window motor, and my dual e fans (would understand that one because they have some serious draw) i thought it was probably just the gauge wearing out on me but i hooked a meter to it and it showed the same thing. its my daily so i dont want to just start tearing into things if there is a simple solution. battery and alternator are about a year old. Also has anyone used the grounding kit and seen results? asking because i want to get a decent sound system in there and do not want it to kill the car lol

Make sure your running all the right fuses, check your fusible links.
My advice, if you want to run a mean stereo buy a good battery and a higher amperage alternator. Ever looked into capacitors?

The voltage gauge on the N/A is junk for the most part. For anything beyond the most basic assessment of the charging system you really should be testing with a load/loaded battery/charge system meter. The drop you're seeing is normal and a ground kit isn't likely to accomplish much. It won't hurt anything but make sure you don't actually create an offset somewhere. If you're really worried about it there's a certain year alternator from the MKII MR2 which is 130 or 150A or you could drop in a higher amperage alternator from an automatic equipped turbo MKIII (100A, I think). EDIT: I can't remember which year MR2 though, and you have to swap the pulley for the one on your alternator. It's got to be got the model with power steering. It's electric power steering, hence the big ass alternator.