Wild afr fluctuations at WOT

[Boosted90Hardbody]

Over the last 2 years I've been fighting an uphill battle trying to maintain a stable afr at wot. I've read every post on every forum on the subject, or related subjects, but the (not quite) infinite knowledge of the internet has not rendered a solution. I've replaced my wideband gauge and sensor three times now, adjusted every setting in TS, checked high speed tooth/trigger loggers, checked every single damn ground, rewired everything I could think of that might help, nothing has made a noticeable change. Figured it's about time to start a thread to try and get some help. Here's my setup:

1990 nissan d21
Sohc ka24e
8:1 wiseco pistons
Eagle rods
Mspnp2 ecu running sequential injection
Deatschwerks 800cc injectors
O&j stage 1 hydro cam
Pioneer valve springs
Martin industries adjustable cam gear, 6 deg advance
Wahlbro fuel pump(not sure which one, boss gave it to me)
China special t3/t4 5456 .63 ar turbo
Aem 30-4110 wideband sensor
Hks ssqv bov

Things I've ruled out:
Injector latency
Coil dwell( unless it's supposed to be over 5.5ms, didn't test any higher than that)
Oil contamination in intake through pcv( had some, none since new catch installed)
Fuel pressure seems steady(3.5 bar at idle 1:1 rising rate fpr)
Duty cycle and pulse with are steady, max 65% duty at 20psi boost
Fuel and spark tables are smooth af
Signal from cas is clean af
Injector timing(could be a factor at such low duty cycle, I've tried changing quite a bit, no improvement)
I have developed a slight exhaust leak pre turbo, afr from previous data logs show the same fluctuations, I doubt this is the problem.

Here's a snap of a run I did on the dyno last weekend

I'm straight out of ideas, has anyone ever seen afr fluctuations like this?

[R34SR]

So the sensor responsible for measuring the AFR content of your exhaust gas is fluctuating.....but you have ruled out the exhaust gas leak pre turbo/pre afr sensor as the culprit....


Where is Tiny T when I need him....

Anyways let me not be "that guy" that turns this place into zilvia.net.....please fix your exhaust leak.