lots to reply to but after work i had to fix the oil pan on my MK4 VR wagon because its my daily and i need it. but after that i was able to mess with the S13, didnt get as much done as i wanted but i learned a few things.
fist of i fixed the lack of power to anything problem! while in the engine bay i found a huge wad of electrical tape. if i poked that wad id regain power to the interior for .03 seconds. pulled all the tape off it and the deeper i got the crisper and stickier it got until i found this:
https://photos.app.goo.gl/sJiYu15xxQxD4TRH6
i will pick up stuff to fix it correctly tomorrow after work, for now i made sure everything had a solid connection. and it works.
so as of now i have replaced the coolant temp sender for the ECU.
ran into the same problem. car cold starts fine revs smooth, builds boost, etc. i measured the voltage cold at 13.8V. im happy with 13.8. once it warmed up same problem. wont rev past 1k. i measure the voltage again at this point at 12.4V. that really really bad. im not saying the alternator is the problem. but it defiantly needs to be replaced. i picked up another. removed the old one, and couldnt get the SR pulley off the alternator. tomorrow i will get a puller and worst case drop it off at my machine shop to get it taken off.
i'll report back if it changes anything. thanks for all the feedback. i really wish i could respond to each one but it would take me hours.