How annoying! My volvo 940. She comes on boost and pulls slowly up until 3500ish, then shudders and the boost completely drops off, and then I've to stop accelerating in that gear. It's stock bar the airbox is off and there's gauze over the Air flow meter. Is there not enough restriction or something? Or is it a boost cut? Or or??? I've no clue bout volvos, please help, it's stopping me from drifting! Thanks guys