Hi everyone, I’m finally getting back to working out some bugs on a fresh rebuild in my 87 turbo. It’s an S5 keg with all the S4 accessories. Had it rebuilt, resurfaced and ported. At the same time I upgraded to a BNR stage 3 turbo, parallel fuel rail mod with new regulator, 720 injectors and an RTEK ecu upgrade (which I now regret). So I changed a lot at once. I’ve got it running pretty good, under acceleration it makes good boost and seems smooth. Problem I’m trying to figure out is I get a bad stutter when trying to maintain speed. (Closed loop?)


Acceleration and deceleration is fine, just when holding the throttle at the same point and not under load. From my searches I’ve found the tps is a usual culprit, but ive gone through that adjustment over and over and it doesn’t change. I tried it set at 1k resistance with the DMM method, and also using the RTEK initial idle setup. When I adjust it with the RTEK it ends up way over 1k to bring it “ into spec”. The idle is also kinda lumpy sometimes, not sure if thats because of the porting or the same issue. It also only pulls 10psi vacuum at 750rpm which is 4psi lower than before the rebuild, though haven’t been able to find any leaks. I’ve checked timing multiple times, and have also been playing with the fuel pressure, right now it sits at 30psi at idle. I data logged it today and will attach the screenshot of where it acted up. The tps seems to track smooth, but the o2 spikes up and down when its stuttering. Can anyone point me in the right direction of what to check next? Thanks in advance.