pull a learning view, post it up or tell us what your airflow learning trims are. if you have an intake thats not scaled properly(or injectors), or not good enough it can affect open loop (wot) fueling. one way to see if the learned trims are screwing with things is to reset the ecu and do a pull and see where your AFR's are.
they say readings at the tailpipes are .4 leaner AFR than what you'd measure at the turbo/downpipe area. Another thing that can cause richness under boost is a boost leak. if air is leaking out from somewhere, the ecu is going to command fuel for a targeted boost ASSUMING the engine recieves that boost. If it doesn't, it has all this fuel and nothing to do with it.