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You have the TB-IAC pressure tap installed?
2.5" intake tube? <-- thats an odd one
Low restriction exhaust?
The BPC is completely isolated?
TBTC mod?
Viggen IC or compressor discharge silencer removed?
Above two items are really needed.
What APR are you using. One designed for shop air use will have regulation problems in a low pressure application like this.
Boost cuts: You have to back the setting off a little bit. Jeff has the most experience with the MBC+A (I do not have a vehicle that can use one). Again, what APR are you using?
How do the plugs look and gap? Might be some timing hunting issues going on.
Check that hose joints or BPV faults are not the problem and dumping air at the higher pressures.
Plug problems and the DI might be dancing as the ECU seeks to kill knocking conditions. Perhaps the plug is too hot. Injectors and combustion chamber clean and premium fuel? Need to elimate potential for these octane effects. Suggest 7ES plugs gapped at .035 - .037". May be too hot for 6ES plugs.
The TB-IAC pressure tap setup would be the most potentially unstable configuration, but it yields the best high RPM boost levels compared to other configurations. But, otherwise, your pressure hunting is not reported by others. Once the system gets on boost, the APR will exit the stage and it should not be a factor. You must use a non-relief type APR or such problems could very well be the result. The MBC+A with the appropriate APR, with or without the TB-IAC perssure tap, is a very stable arrangement. Your fuel cuts are related to this instability. I would down-set the boost a bit until you solve the hunting, then after that is resolved, you may be able to set to higher pressure.
posted by 68.93.19...
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