if the cars stalling, from my experience, the fmic should have nothing to do with this saga..
perhaps, check with your tuner about these few things..
- b.o.v could be leaking,
- fuel pump maybe earthing
- if its a series 1, rb25det, check you coil packs & the ignitor pack above the #6 coil pack
- crank angle sensor maybe ****ed, & might need replacing
* my car did this, i though the b.o.v maybe leaking, but that wouldnt cause your stall
- my cars crank angle sensor was not sending the right signal, & the ignitor pack was ****ed as well, ive replaced both c.a.s & the ignitor pack ( as we speak its in shop) & the mech said thats my problem, maybe yours too...these are just a thought...