car runs and performs well until accelerated in high gear from low rpm then perfomance seems to go into limp home and is much restricted.bmw fault codes 4501 exhaust gas recirc control deactivation(p0401) and 4530 charge air pressure control small turbo control deviation are set and clear until the next acceleration under "load" is performed.air flow meter has been changed(bosch)and modified crankcase breather alongside air filter has been fitted.disconnect and plug vac pipe at egr valve the car performs well at all loads and no fault codes reappear.connect vac guage with t piece at egr but never seem to get full 20" vac and it varies with load but i am unsure what results would be normal .be grateful for any inputs or further tests i can do .thanks in advance paul