I replaced the p/s pump on my EXT last fall.
A royal pain, to be sure.
I hope you installed an
ACDelco 88963604 GM Original Equipment Power Steering Pump.
I would use nothing less for this.
A former mechanic had replaced my bad OEM pump with an aftermarket pump many years ago and it whined the whole time until I finally had enough and replaced that one with the ACDelco OE pump.
Also, use only
ACDelco Power Steering Fluid 10-5073 with NO additives.
Ever.
I stumbled across a Youtube that described a one-man procedure to flush out the p/s fluid using the old pump before you remove it.
It worked great.
I found getting to those hidden bolts to be the worst part of the project.
And pulling and reinstalling the pump pulley will have you learning some new cuss words.
And for reasons I will not get into, I had to do those chores twice.
On the chirping note, I chased a chirping sound on my EXT for some time before I finally figured it out.
I had replaced all of the usual suspects, pulleys, tensioners, and belts.
I bought name brand belts and nothing helped.
Until, I installed a set of Goodyear Gatorback belts.
Goodyear no longer makes the Gatorbacks, but Continental does.
Continental OE Technology Series 4060922 6-Rib, 92.2" Multi-V Belt is the main belt and
Continental OE Technology Series 4040377 4-Rib, 37.7" Multi-V Belt is for the a/c.
Now, these are the only belts I use on my 2003 Z-66 and my 2004 EXT.