Do you honestly think the idle adjustment screw is supposed to be all the way in? That's what it's there for, to adjust the base idle speed. Even if it's all the way in, it still lets a small amount of air past the throttle plate, creating a "small vacuum leak" in your words. If anything, if you have the screw turned all the way in, and it's still idling at around 600, it's actcually idling a bit high, since most cars will stall out with the screw all the way in. Mike brings up a good point about the IACV. If you're trying to set the idle speed with the IACV connected, you are not going to get a consistent idle. The IACV raises idle above the base idle set by the screw. The IACV controls how much additional air is let past the throttle plate in order to raise idle speed to warm up the engine faster. If your car is dying when you come to a stop, it's probably because you set your base idle with the IACV connected, and then when you start driving, the engine warms up. When you stop, with the engine warm, the IACV shuts off, and your idle speed drops to the screw setting, which is obviously low, since you have it turned all the way in. If you want a consistent base idle, you have to set it with the IACV disconnected. It wouldn't hurt to jump the service connector as well. If you throw an IACV code while setting the idle, just reset the ECM afterwards. If you feel setting base idle speed via the factory adjustment screw is a "ghetto fix", then I guess I can't help you.