im having same issue...so i did what u said and unplugged the line from solenoid to bbv and i get full boost but only after 4k rpm below i wont get no boost at all so connected back the line and back to how i was i punch it and gets half boost even in low rpm wot but stays half ways in wot shift where as disconnected i got full boost on wot shifting but no boost on low rpm...what can i do to fix the problem? replace bbv? or bbv solenoid?