Definitely sounds like AFM. Unplug it and see if the car runs the same.
Try this:
http://www.skylinesaustralia.com/forums/topic/113284-fixing-your-rb26-afms/
Well when water comes out something has to take its place. What takes it's place is air, so bleed it and see if you still have problems.
Edit maybe not enough in the first place? Is there any smoke coming out of the exhaust once the car is warmed up?
If its an r180 diff in there you'll have to get an r180 lsd or change the rear subframe. Also, depending on the LSD you get, you will have to change the halfshafts to suit. Get a mechanical LSD.
Grease the regulator, check the brushes inside the window motor, WD40 or CRC the the window sills and do this tutorial. Pressing the clicky things with you fingers, they will make the window go up and down.
Good luck.