Belt noise. Chirping/squealing pulleys maybe?

[Rbrinton]

I will try to keep this short

Right now when I drive my vehicle. There is a noise I will classify in the chirping category, although I am not sure that is accurate. It's not a belt squeal but seems to be longer in duration than what I am picturing as a chirp and it does not seem to change much as the car accelerates versus idle. Except that it only seems to happen or is audible when driving at slower speeds and between 600 and 1500 rpm. It so far has not happened at startup but begins shortly after I begin driving. On the surface streets it is there almost constantly but once I am on the interstate it does away and will usually stay that way until I next drive the car. However yesterday it came back after getting off the freeway but once again disappeared as I pulled into the driveway. Needless to say this is making it difficult to get in the engine compartment and look and see if there is a visible cause for noise.

Here is the history since I bought the car 6 months ago

2002 GXE 110k miles

@108k miles took in for a service and inspection. Standard oil/filter. I was told it needed new drive belts, so I had them replaced. After they were replaced I was also told they couldn't tighten them enough to stop the squealing because the idler pulley needed to be replaced and that would be almost $600 and they did not have the part and would have to order it.

I drove it for 1 week, bought the pulley and replaced it myself for $35 and 45 minutes of my time. Also changed spark plugs because the needed it and were causing misfires

Problem fixed

@ 109,500 miles an increased clicking noise that started shortly after I replaced the pulley, which I thought was a lifter tick, changed to a horrible squeal. Discovered that the harmonic balancer had separated and needed to be replace. Ok got that fixed and replaced the crank seal while there.

And now I have this new chirping/squeal noise that doesn't quite seem to fit in any of the categories of worn belts, squealing, or normal chirping, pulley misalignment.

Any suggestions on where to start?

Also off topic the car runs pretty good except at startup it will idle at about 1300-1500 rpm until it begins to warm up then drops to 800 rpm or so until it gets to full operating temperature and been driven a little then while in drive at a stop light or something it idles around 550-600rpm and a bit rough.

Any ideas on what is the cause? I am thinking EGR but not too sure where to start or if that would be a good place.

Sorry didn't keep this very short.

Thanks in advance.