Well, I can tell you Toyotas have been know for their problem with MASTER CYLINDERS. I've had a lot of Toyotas and I've noticed this to be of concern, especially with Celicas. Master cylinders aren't that cheap to get, but if you've replaced everything else of major consequence, I would be pretty confident that the MC needs replaced. Also, you might want to try to adjust out your rear brakes as well, especially if they are drums. Hope this helps.