http://shbox.com/1/egr1.jpg

In that picture, it's right below the EGR valve, and above the coolant crossover pipe. It has a black rubber boot connected to a hex bolt-looking thing and a wiring connector on the other end (not connected in Shoebox's pic). What is it? On mine, the rubber boot is torn partially, is it OK if I glue it back together somehow, or should I replace the whole thing?

 

I think you're talking about the oil pressure sending unit. Thats the only thing I see thats between the egr and coolant pipe. Does your oil pressure gauge work? Does it leak oil?

 

You just had to scroll down a few lines on Shoebox's photo list. I don't see a rubber boot... do you mean the plastic body of the sensor has a crack in it? If so, it needs to be replaced:

 

Thanks, that's the one. It is the plastic housing that's cracked (not rubber, sorry), so I guess I'll see if I can pick a new one up someplace.

 

Get a new GM piece if you want the guage to be at all acurate. I got one from Autozone and it moves the needle but thats about all I can say for it.

 

how hard is it to change that sensor with the engine still in?

 

I had no problem, but I had the intake manifold off when I did it. I don't think it would be too hard with the intake on though, you might just have to move a few things.