ShimiBoi

like the title says i have a small problem, plz dont flame me...i did search and found some things that might help and tried them with no avail so any help will be appreciated
things that might help you help me:
nearly stock ka24de with
-intake
-secondary butterfly delete
-cat-back exhaust
-msd blaster ss
-new ngk iridiums
-new ngk wires
-new cap and rotor
-new ignition coil wire
-throttle body spacer
-working egr
-connected aiv
-fuel filter replaced about 5k ago
-s13 auto ecu on stock manual s13.
-stock injectors [email protected] ohms [email protected] ohms [email protected] ohms [email protected]

problems:
-at start car is very hesitant and doesnt want to go, but doesnt misfire...just kinda bogs down until about 2500rpm (cold start).
-after it starts going car seems to run well under load.
-while decelerating with very partial throttle (ie. to slow the car down but not too fast) in gear car misfires
-at ~2000 rpm (while decelerating in gear) misfires several times and car gets a lil jerky.
-in neutral and revving up car will occasionally misfire after 2k
-under full throttle no misfire is noticed
-gas mileage has dropped from ~26 to ~24mpg (due to the auto ecu i presume)
-starts up fine even when cold

thank you zilvians for your help ahead of time!