Jiffi,
Have you set your base idle speed? I'm pretty sure it should be around 750rpm, not 600RPM.
Check the FAQ under Fuel injection/throttle switch and throttle body adjustment.
It tells you how to set it. You can make a test LED for 2 or 3 bucks with parts from radio shack. If your O2 sensor is ok, throttle body clean, no Vacuum leaks etc, Calibrate you AMM and set base Idle as in FAQ. If all this is OK, I would suspect dirty fuel injectors. If they are slightly clogged, they will perform at higher speeds as pressure forces the fuel through. When you stop at a light they will sputter and not give a proper spray pattern to maintain a proper smooth idle.
If your Idle is also set too low this could be enough to cause a stall fom gas starvation. To add to this, if your brake booster hoses are bad or the one way valve at the booster is leaky, it can cause your idle to drop when you apply the brakes. I beleive that power steering vacuum can also cause this. Hence with the wheel cranked and the brake on it stalls.

740man