Squeaky Belts!

Hey guys, this is my first post! I’ve got a 92 lebaron with a bone stock Mitsubishi V6 engine. Recently, due to my own stupidity, I lost my engines crank pulley (it flew off in my driveway during idling, I had taken out all the screws to remove the A/C pulley and the only thing holding it on was a small metal tab). After putting it back on, I thought it would be a good idea to give the belt system a good once over. My old tensioner was pretty much locked solid so I replaced it with a good quality goodyear tensioner. The new tensioner came with the instructions to reuse the old belt and so I did. Everything was good for a week or so and then the belt began to chirp. It would only chirp around 3k rpm and higher and sounded like it was slipping. Since it had laid in snow (and likely oil) for a while and had some belt dressing on it, I took it off, lightly sanded all the pulleys and cleaned them with a degreaser and installed a new, identical brand belt (Dayco). The noise went away with the new belt instantly. I, an idiot, smiled, thinking that my problems were gone for another 60k miles. I couldn’t have been more wrong. The belt began to squeal again after 4k or so miles. Just turned the car on one day and it was there. It was colder than usual and the next day it warmed up and poof, noise dissapears. Now After another 400 or so miles, the noise came BACK and is a constant squeak that never goes away. I checked the tension and the alignment of all the pulleys. The tensioner is doing its job, the pulleys are all straight and the belt itself shows absolutely no signs of wear except for some EXTREMELY minor fraying around the edges. I’m tempted to go and get a belt that is .5" longer and put it on because I have found that if I release a tiny bit of tension from the tensioner (with a wrench while the car is running, don’t try this if you like your fingers) the squeaking stops and the power steering and alternator seem as chipper as ever. Any opinions and comments are greatly appreciated as it is loud and embarrassing! Thanks!