I would remove the MBC and Intake completely.
You have added to many mods that truly require a tune. I'm not 100% sure but i believe even the TBE needs a tune for the 06 to run properly but even more so with an aftermarket intake.
For my 05 the stock PSI is 12.5 so even your 15 seems really high for a stock mapping.
Maybe go back to stock and see if everything is better. Than add the TBE. Run that and see. But stop there until you get the Cobb AP. But even then those OTS maps are not designed to have a MBC or aftermarket intake other then theirs.
Hopefully someone chimes in if I am wrong but that's what I would do.
05 WRX Wagon - 333 AWHP / 275 WTQ