With the IPR not plugged in it will remain open and bleed off the pressure, it needs power to close it to build pressure. Did you remove the IPR and test it with leads to a battery to see if it is actually working. Also note that it is very common for the IPR to get clogged again after a new HPOP is installed. The pump cover and pump can be removed without taking the intake off, it is definately harder but it can be done.

 

I just replaced the ipr, but I didn't test the new one before I put it on. I was wondering if I was actually getting signal to the ipr or if the ipr is actually closing. Since I am seeing very low psi it was a thought. Unfortunately I have an O shaped intake instead of the later U shaped intake. I don't think you can pull the pump with it on.

 

I can't remember if I took mine off with the old intake or the new one, I had the same as you. Also there is an oring on top of the pump that seats in the cover and if that gts torn it will do the same thing. do yourself a favor and get a late 04 and up intake, you can get them on ebay for $85 and sometimes you can even get one with the stock elbo from 05to07, they flow better then the early ones and bolt right up. it also gets rid of that nasty butterfly valve that some of the early ones have. It make life alot easier, you can even get to the IPR and ICP without to much problem. If you do an egr delete then you can even cut the mounting tab off that the back of the EGR cooler bolts to and that will allow you to remove the intake without removing turbo, I've done it and it realy saved time when doing a oil cooler.