I've searched and every link dead ends with someone trying something and then never posting a solution. So here's a look at what mine is doing. Idle is ok sputters a bit every once in a while but mostly ok. If I'm cruising it'll be very hesitant to do anything and sometimes the motor will pulse while i'm driving. Once I hit boost everything is fine but it stalls sometimes when it's building pressure. I have it set for 40psi and it bounces over and under.

s4 6-port turbo motor with a streetport. Walbro 255, rtek 1.5, 550/720 injectors
No emissions...etc.

 

what kind of fuel regulator is on your setup?

 

AEM knock off....

I bypassed the resistor/relay stuff and it seems to be ten times better. We'll see if it stays good tomorrow.

 

id bet FPR, good luck

 

Just another quick question/..WHERE is your fuel regulator located?..BEFORE the engine?
..My thinking is that IF you had it BEFORE the engine it would have a hard time maintaining Steady pressure because the Injectors are always opening.(bouncing pressure).
I have my fuel set up as a Parallel rail system and the regulator is AFTER the Fuel rails..the Pressure is Rock Steady.

 

I had I VERY similar problem. Fixed it by bypassing the fuel pump relay/resistor also check it out!

https://www.rx7club.com/nw-rx-7-forum-33/name-fuel-pressure-issue-870743/

I thought reusing the factory plugs and spades was slick and clean...

 

on my s5 its on the end of the secondary rail