Another thing that affects straight cuts, is the distance between the roller guides front and back. It is good to have them set no wider than necessary to cut the size metal. There is more tension in the blade when having a smaller distance from front and back guides. The problem with adjusting that distance from work piece to piece, is that the blade angle changes. The blade guides have to twist the blade as it comes off the drive wheel to get it perpendicular to the saw table. Not sure I am clear about this. The blade guide closer to the drive wheel has to twist the blade more, the closer it is to the wheel. The blade guide at the idler side should also be adjusted in toward the work vise to narrow the gap, and alleviate blade wander.

on mine, I normally cut smaller pieces, so I have the distance between front and back guides set in the area so I don't have to move them. That way I can adjust the rollers (bearings in my case) accurately to maintain a vertical cut.

ken