Chirp/Squeaking Belt
 

I have the 98 northstar, sls. I replaced the (it has a bunch of possible names) guide pulley-the pulley right between the alternator and the tensioner, its just a simple pulley with a dust guard. it started squeaking/chirping and i figured out which one by spraying a little water on it.
Its a real bugger to get in and out, and its still making noise, and the belt is also (i can see rubber on the pulley from the belt sliding on it). it seems to be the dust guard making the noise. I put a little grease in the inside, the out side piece (looks like a washer bent into a hat shape) has rub marks on it i think that is where the noise is coming from, The belt is riding right up against the outer rim of the pulley, i believe it is misaligned, but i dont understand how it would have gotten out of alignment, the parts match exactly in every dimension and detail, even the shape of the pulley's front end and the bearing is also an exact match according to the stamps (the seals are even the same color) on them and a visual check. And i used the same dust guard/assembly and bolt to put it back on...by the way this bolt does need antisieze? and should be torqued to 35lb right?
So i have a spacer i could put between the dust guard and engine block that would put the pulley in the center, but i am no mechanic, what should i do?