It's worth diagnosing the electrical system.
the window switches use a couple of relays to send power to the motor. Those relay contacts can sometimes get a bit weak due to their location in the door. This isn't an uncommon problem in the Supra, for one. Unplugging the motor itself and using a multimeter can show a difference in voltage between "up" and "down" positions of the switch. If there is a difference, you need to diagnose both.
If the problem is mechanical, you will likely hear/feel it. The window motor will sound more strained, or there will be vibration in the window as you move it up. The window won't take much mechanical resistance to movement, the motors have a circuit breaker which turns them off if they're over strained. They shouldn't crush your finger if it gets caught in the window, for example. So an issue with speed is more likely to be electrical than mechanical. (It's still worth it to use a bit of graphite lube in the window tracks now and then.)
