ok so here's the rundown



car has been running strong up unitl a few days ago. for some reason or another the car will not tip-in or have any low rpm throttle once it hits secondaries which is an event unto itself.(lots of stumble and fumble it doesnt drop out entirely)



assumed it was the P injectors and found the car had been running on LI injectors for the year that Ive owned it(came with the car) without an resistor pack. S injectors were low inpedence so no big deal.(also swapped the ecu with a known good one just in case)



problem stills persists



since then Ive checke every electronic device on the car that influences fuel delivery to no avail.



fuel pump: swapped it to an FD pump X

fuel lines and filter. changed filter lines were good X

checked AFM: good IAW the FSM

checked reg: havent done tht yet but as i said, the car does fine above 3700rpm

TPS: good

primary injectors: metered good . they spray fuel (did the mazda "poor man's flow test") still weary will probably replace.

checked harness: continuity to inj., coils, inj.12v and all sensors is good

grounds: good but redid them anyway. all meter less then 1ohm.



tested SAFC that was installed and has functioned properly for about a year now: tested good with proper setting and set to zero correction for testing and diagnosis purposes.



tested for possible vacuum leaks or mechanical failures: non so far



my only guess now is the regulator (wont go over 38psi )has crapped out or there is an electrical problem that eludes me.(ignition system?)



any insight would be appreciated



1988 s4 N/a

third bridge

fd fuel pump

oem primaries 550cc secondaries

sequential ignition mod

no pulse damper

no emission equip.

RB header



ps if this a re-thread i apologize in advance. my internet crapped as i attempted the first version of this thread.