Have been searching and haven't exactly found identical symptoms.

My x5 is a 2004 3.0, recently had idler pulley changeg with new belts and new alternator.
While driving if im flooring it or just speeding up it'll kind of go limp, and idle begins to sputter and will lose power (pickup and can no longer speed up). I've revved engine while in park and no sputter only happens when in drive.

So far I've checked belt, and am currently about to clean maf and have checked for leaks in exhaust as well.

Has anyone had this happen? Or insight?