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Having same problem, with basically the same set up. the stutter hits when my WOT switch closes at about 3/4 throttle mainly when rpm's are below about 4k. If above 4k rpm, the boost is steady, albeit somewhat tapered. I did not have the problem previously when the knock sensor cut the boost, I think because the knocks cut the boost before the WOT stutter could be felt.
Posts last week described the AMM and the rev pickup combining to trigger an ECU controlled fuel injector cut off and not a fuel pump cut off. I'm not sure if that is correct, but the stutter is not the same as the rev limiter fuel pump cut off.
I tried a 0-1k ohm variable resistor cut into the orange wire from the AMM, which is supposed to fool the ECU into thinking that there is less air mass flowing. This resulted in severe backfiring as soon as the resistance was over 100 ohms. Brad at Georges in Kansas City, says that the resistor trick works only if you are using 30 lb injectors, and I'm running 24 lb inj with the rrfpr at 3.5BAR. This is not logical to me, so Brad and I will try to sort this out over the phone.
The next thing I'm going to try is to cut the WOT wire at the throttle position switch to see if that fixes it. I would rather not do this permanently, because I'm not sure if the O2 sensor can call for enough fuel enrichment at WOT. Supposedly at WOT, the ECU is operating in an open loop control mode, setting mixture from the AMM signal and not the O2 sensor. Perhaps with the rrfpr and 24lb injectors there is enough juice to avoid lean problems, even in closed loop off the O2 sensor.
If the WOT throttle switch wire cut does not fix it, I'll try new plugs just for the hell of it, but I think that the problem is fuel related and not ignition. I'll post my results, please do the same. Thanks
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