Sadly; most M22's that are noisy, are usually M20 or 21s with either poor quality aftermarket gears, used parts, a worn out case or all of the above. If you want to keep your 4 speed (as as long as the case doesn't look trashed upon close inspection theres no reason not to); I would build an M20 if its a M20 or 21 platform. If it really is an M22; I'd clean it up, sell it and start from scratch with an aftermarket M22 wide ratio gearset, with either 3.73s or 3.55s in the rear.
you can put your trans in 1st gear, turn the input 10 times, count the number of times the output turns. If it turns 25 times, its an M20 (2.52 1st gear). If it turns 22 times, its an M21 or M22 (2.20 1st). If its an M21 or M22, you'll have to remove the sidecover and look at the helix angle of the gears to decipher what you have.