hey so if i buy an afr and i can monior my airfuel but cannot alter it (like with an safcII) what are some manual ways: mods, blockoff plates/ valves i can remove or whatever, to lean out my air/fuel. "
also what are some avg numbers as a reading??(on an afr)
how lean can/should i go??('87 gxl)

 

One option you have on the S4's is the AFM flap spring.
Be careful not to do anything you can't undo.
If you increase the tension on the spring, the door will be further closed at a given air flow, so the ECU will feed less fuel.
The effect is non-linear, so it will lean idle & light throttle tune more the open throttle tune.
Another option is to lightly sand about .010" (not over .020") off the outer edge of the flap door.

Numbers? I went for 14 at no load at 1K and 2K, then let it go richer above that.

The big deal with a narrow band AFR gauge is being able to see if and when you're in closed loop, and when you get deceleration fuel cut.