What are the 2 tensioner pulleys called?

[Shades]

Hi. My pulleys are squealing mainly when gas pedal is not pushed in. Changed both belts. Still loud. Removed all three pulley wheels and a piston looking thing that was attached to one. I think the idler wheel?, on bottom left with one simple belt is good. The other two wheels are free spinning and need replaced. The only Visible difference is the bolts that fasten to them and one has a larger mounting spacer. So how do these 2 differ and what are they called? Thanks guys.

[zoner]

The pulley with the piece that looks like a small hydraulic shock is the belt tensioner (your car must be a '95), the other one is the idler pulley. Occasionally, the hydraulic shock will seize and slowly elongate the bolt holes on the shock and ultimately cause premature wear on the pulley. With the belt tensioner pulley installed on the car, you should be able to apply pressure to it and it will compress slightly. If it does not, it's time for a new tensioner and it's probably best to replace the pulley as well. You're best bet would be to replace all three pieces (idler pulley, tensioner pulley, tensioner).

[Shades]

Thanks, yea my car squeals so. Loud. It comes and goes. Usually when I let of the gas or sit it squeals. When I turn the key off, it squeals for a split second afterwards and belts aren't moving. So it might be something inside? I'm stumped.

[Shades]

Update: so after regreasing synthetic on pulley wheels, all three. I took both belts off. Fired it up for just a moment and it still squeals loud. So I narrowed it down. The only pulley wheels moving is the big one at the center bottom that goes into the motor or somewhere.