FOUND THE SOLUTION to the squeaking noise after hard shifts.
I have had this problem since 20K+ miles and slowly but surely getting worse... I am at 43k miles now and can reproduce it almost everytime I step on the gas real hard. I took it to the dealer several times and they check the belts and the tension and it was fine so I had to go back home sad/angry everytime. Until my dad told me that belts tend to "crystalize" after a while, specially with a lot of heat. He told me I could lubricate the belts to help with the problems.
I went to Advanced Autoparst and got a "Belt Conditioner" can. It is red with a black cap. It is similar to a WD-40 can with the little red straw to direct the spray. I took out the engine cover (Plastic with Mazda logo on it) and unscrewed the coolant bottle and moved it out of the way (WITHOUT disconnecting the hoses). This will let you see the belt much better. WITH the engine off spray the interior part of the belt (wavy part) the best you can and spray some extra on the A/C pulley area since the squeaking only happens with the A/C on, at least in my case. Then I turned the car on and the A/C for about 3-5 minutes, shut off and spray some more.
I took the car for a spin....I floored it the best I could with the A/C on and no music....NO MORE SQUEAKING!!! THe can says to repeat every 3K miles...I might do that. GOOD LUCK GUYS! [/b]
Yep, that will work......for a while. you have two choices: repeat this every 3k miles or so until the belt breaks, or replace the belt now. Keep the old one as a "just in case" spare and enjoy the silence of no more squeaking. The noise is most common with the A/C on because the compressor takes a fair amount of force to turn, putting a greater load on the belt. Because the belt is old and has dried out a bit, it slips on the compressor pulley and squeals.
I dont know if its even a problem with the Mazda line but some of the mid 90's GM LT1 motors had a batch of bad tensioners, even a brand new belt would slip and squeal, but it sounds like its the belt just getting worn out in your case.
I like the Goodyear Gatorback belts, nice agressive pattern on the drive side of them.