I've been running an MS v3 as per Braineack's write up in parallel for about 4 months. It is running Hi-Res since 10d and has been pretty solid.
The car is running stock HKS wastegate pressure (MS has been modded for EBC, but no solenoid has been installed as yet). It is a 1990 with the Standard TPS, standard injectors (i know, i have some 330's to go in).
Other than that, I recently changed the pcv valve from the standard mazda one, to a metal can one from an old Ford, but reverted back to the standard one as it held up under boost better than the Ford one
What has been hapenning recently is, after acceleration under a significant load (eg 3rd gear or higher) the MS sort of hits a rev limiter, then starts to idle very badly with AFR's bouncing all over the place.
What is really weird is that the car has been fine for quite a few months and relatively unchanged since MS was first installed, apart from the MS cap mod for Hi Res code (I did it pre empting the rev limit problem rather than having one, so i am unsure if it would be present without the cap in there).
It seems similar to a problem experienced when a fuel filter is blocked or the fuel pump pressure is low, fuel filter has been replaced and fuel pump checked.
The log shows it running smoothly for the first half, then as i pulled onto the motorway and ran the car well in 3rd gear, the rev limit weirdness started and stayed there until i got back home.
I've checked for vacuum, fuel leaks, all wiring. Nothing jumps out at me.
Any help would be appreciated.