2006 XC90 whistling noise
 

I am a newbie to this forum, having just purchased a 2006 XC90 2.5T with just shy of 100k for my wife. We bought it knowing that the vehicle had a whistling/squealing noise that happened every time you started it cold but went away when it warmed up. I assumed it to be an old sepentine belt that I could handle myself. Well, on top of finding out that there is no printed repair manual for these cars (an unpleasant surprise), I found that the noise actually seems to be coming from somewhere on the driver side of the engine. It sounds like it is on the firewall side, though it's hard to pinpoint. It is only loud during the higher RPM at startup and during acceleration, and it goes away after running for 5-10 minutes. My wife has tasked me with fixing it...or having it fixed if I don't fix it in a timely manner. I have read about vacuum leaks and oil trap pans that could be the cause. I've cracked the oil cap to see if it went away with no luck. I'm having a hard time tracing the sound, and without a repair manual I feel a bit lost. Some direction as to where to look and what to look for would be greatly appreiated.

I'm bumping this post of mine to see if anyone can help. I've just about decided I have a vacuum leak somewhere but just need to find it. One note is that a few times while on trips my cruise control has shut off and won't reset until I turn the vehicle off and back on. Is the cruise run by vacuum? Could this be a hint to where there may be a leak?

Also, side note...the other day while under the hood I noticed on the plastic trim in front of the windshield over the firewall, there is a molded "Rotary Engine" badge. This is a 2.5T, which is a 5-cylinder piston engine...right? Does Volvo even make a rotary engine?