Swapping in late model (1990? and later) upper plenum and throttle body sure cleaned up my idle issues. HUGE improvement in idle quality, and a noticeable boost throttle response and power.

The older style parts can probably be made to work well using tips provided here, but the newer style is a much improved design.

EDIT: I see in your sig that you have an 89 truck. Maybe you already have the later model plenum and throttle body, in which case my points are moot.

Last edited by riverrat; 09/18/07 04:35 PM.