Squeak from front of car

First I would run the engine with the belt removed, just long enough to verify the noise is gone. As an alternative, dribble a little water onto the smooth back side of the belt while the engine is running and the noise is occurring. If the squeal changes, the typical cause is a pulley is turned or tipped a little. That will make the belt walk across it as it goes around it, and that is what causes the squeal. Fraying on one edge is another clue to a pulley problem.

If you look straight down to the upper area of the belt, you should not see it peeking out to the side on one of the lower pulleys. That can be hard to tell, but if the belt is off-center by as little as 1/16", that's more than enough to cause a squeal. Also, the pulleys were painted black originally. Look for any pulley where the worn, shiny area is peeking out due to the belt now running to the side a little. Either that pulley or the one right before it is turned or tipped.

Tipped pulleys are usually idler or tension-er pulleys riding on a bearing. The suspect is less likely to be the power steering pump, generator, or AC compressor.

Squeaks come from things that are moving, and that can include loose parts that are rubbing against each other. If the noise is gone when the belt is removed, you should be able to make the noise occur by bouncing on the car. Worn ball joints and control arm bushings are the common causes. You should not hear those with the engine running as long as the car isn't vibrating.

Try rocking the engine forward and backward. GM engines usually have a "dog bone" engine mount right up on top, between the top of the engine, and the "core support" that has the hood latch. That bar limits the amount the engine can rock. If rocking the engine by hand, or when shifting between "drive" and "reverse" with the engine running, causes the squeak to occur, look at that bar or the plastic parts in the fresh air tube from the air filter housing. The running engine can make those squeak if they vibrate against each other.

Front-wheel-drive cars have a flexible joint at the front of the exhaust pipe so it doesn't break when the engine rocks. Some cars use a metal gasket in that joint that can squeak. That squeak usually changes as temperature changes. The noise could go away or it could become worse when the engine is warm. When it occurs, you'll hear the squeak each time you shift between "drive" and "reverse".