Intermittent Power steering issue

[EnkZ32]

Hello, I'm new to the forum, and a first time Z32 owner. I just bought the car about a month and a half ago, it's a 93 300zx 2+0 NA, and have been working on it since, and it's coming along nicely. Car seems mechanically sound, with only a few issues that need addressing. It will be my daily driver and I fully expect to complete a motor swap when the time comes, but for now it's got 150K on it and it seems good.

Here is my issue, and I apologize if this has been brought up before, but after a quick search I think what's going on with my car is unique to pretty much anything I've read online. While people have had this issue, my symptoms seem different. Hopefully you guys can help. My power steering goes out alot, I would say it's 60 % off and 40% on. The car drives amazing when it's working. There are a few things that seem strange to me though. I put on some 18X8.5 wheels on it and after having them on it began pulling to the right only when the power steering was not working. If the power steering is working it drives straight as an arrow. There was only a slight pull before putting the wheels on, but not as drastic. I've ruled out the wheels, I switched them around and it made no difference. The other thing I've noticed is very strange. I live in Florida, and in the evening and early morning when it is cooler the power steering seems to work, but in the heat of the day it stops almost every time, so I'm not sure how, but I think the temperature may be effecting this in some way.

I've checked the speed sensor and that seems to be reading with my meter anyway, whether it's working properly or not I'm unsure. My mechanic friend seems to think it could be the pump but that seems to be starting at the end of the line in my opinion. Any suggestions?