Originally posted by DevilDog66:
One difference between the GS300 motor and the IS300 motor is the Power Steering Idle-up Control. If your at an idle, in gear, then slightly turn the steering wheel the idle goes up to help with the power steering load on the engine. The GS300 uses a vacuum controlled solenoid. The IS300 uses an electric idle up solenoid. The engine is made for both cars, but when they send it so the IS300 factory they leave the tube in because it's too much trouble to remove it later.
That's what it's for.