[ischmitz]

Some questions:

Have you checked for vacuum leaks in your intake at all?
Do you run an O2 sensor and have the proper coding plug on the DME harness? (Hammer will tell)
Is your O2 sensor good? (Hammer will tell)

As I said the screw provides a fixed amount of unmetered air and the ICV provides an adjustable amount of unmetered air on top of that. Both will affect the mixture in the same way. By adjusting the screw you shift the regulation range of the ICV by a fixed amount.

The DME adjusts spark advance and ICV opening angle (air) to keep the idle at its programmed level of 880RPM. The O2 sensor signal is used to provide the correct amount of fuel to maintain the proper A/F ratio.