Something on the front belt drive would be my guess. As stated above power steering pump / alternator but it not that try the fan clutch. When they go bad they scream.
Good luck, strange noises are hard to pin down

 

do u have a throttle body spacer? or do u have a little leak on your cai?

 

Possible your low on oil and its your valvetrain screaming at those rpms ?
I have an 02 4.7l and I think I know the sound your trying to describe..
What tune are you runnin on your SC3865 and are you running the correct octane for that tune ?

 

Could the power steering pump really make that kind of a noise? Or just the bearings in the pulley?

 

I have a 2008 1500 QC 4.7 with the same kinda sound perhaps and at same high RPM...my truck is stock except for a cherry bomb catback. Only 9800 miles on the truck since I bought it new last August...I was thinking mine was an exhaust leak...? Bout ready to take it to the shop that put on the system to check it.

Kevin

 

Are u sure it's not whine coming from your speakers? i.e.bad ground?

 

if it sounds like a siren, its the power steering pump. and yes a power steering pump can do that. and yes it can happen only at high rpms.

 

Check your pulleys!!!!!! Mine did it this spring.... it was the idler pulley... power steering pump is also a close bet!

 

I have my chip on 91 performance and Im running 93 octane.

Ill check them out but what am I specifically looking for? And same with steering pump? what are the signs?

No throttle body spacer and I have the stock intake...

I am positive its not the speakers. its far to loud and it comes from outside my truck, in the engine. Thank you guys for all this help too.

 

I would also like to know how to check the pulleys to figure out which one might be bad. I've tried using a stethoscope and so far I've misdiagnosed the problem twice. Anyone know any tricks on checking the pulleys to see which one might be bad?