I have messed with the setting on PFC, adjust TPS, bleed screw etc etc. I have a large street port, and the car likes to idle around 1000- 1100 rpm range. Hoever, sometime when I am decelerating, and put the gear in neutrol, the rpm will dip below 5-800 rpm, and bounces up to around 1500 rpm range until the car come to a complete stop. I have adjust the idle / rpm fuel pickup setting and the idle bouncing is less severe. But how would you stop the rpm from dipping too low? around 1K is preperable. Any advise?

 

The further your mods and idle rpm are away from the Mazda stock standards, the harder it is for the ISC to control idle.

Since you did not list exactly what all you adjusted, here is a complete list"

(1) air flow - TAS & AAS(aka ABS)
(2) rpm - the three Commander ISC idle rpms when using the ISC, if not using the ISC (rpms set at 0) , then #1
(3) fuel cut off - the three Commander ISC idle speed cutoff rpms
(4) rpm de-acceleration control - dashpot slows down throttle closure