Right above the radiator cap (stock 90 TII, with koyo radiator) theres a squeaky noise, like a loose wheel on a red wagon, and as soon as I open the radiator cap to relieve some pressure. That noise goes away.

Secondly, this problem is on and off. When driving, my car tends to drag all the way to redline. On a stock guage it shoots to the top bar, usually it goes a little above the halfway point and stays there, and as the rpm's get higher the boost would start to creep lower. This would happen in all gears, but sometimes my boost would work perfectly like when I first got it. I don't know if this could add onto the problem but about less than a week ago I replaced 3 vacuum lines. They're bunched up on the passenger side of the engine bay a little behind the intake.

Any help would be great.

 

Schnargles.

 

You are removing the radiator cap.
While the system is.
Still under pressure?

That is. A brave move.

If you haven't already, replace the radiator cap.
While you're at it, remove the hose from the upper neck and make sure the aluminum hasn't corroded through.
May as well check/replace the o-ring that seals the cap assembly to the fill neck as well.

As to your second problem...I have no clue what you're describing.

 

My friend showed me first about removing the radiator cap. At first I thought the engine was squeaking because it was old, but as soon as he removed it. No more noise.
Other than that I'll go ahead and try that.

Haha I just read my second problem and it's disturbingly mind boggling. I was just trying to say that the car feels sluggish to redline, on occassion. Sometimes the car works perfectly fine and at other times the car feels really really sluggish, but mostly sluggish.

I need a camera to show you the 3 vaccuum lines i replaced.

 

clogged cats, maybe replace the o2 sensor as well. Thanks for clarifying, I had no clue what the hell you were talking about.