First off I assume you have no check engine light, as you're not reporting one.
How many miles/Km?
Sounds like a couple of possibilities:
Intake boots could have cracks, or not seated properly etc.
2. Fuel pump could be soft failing, and, or relay and filter
3. When you mention sluggish take- offs, I think of cam position sensors, but they would throw a light, and a code. I have experienced sluggish, downright unsafe acceleration, as a result of a failed intake cps (cam sensor)
It could be many things, if you can find someone, perhaps a local fanatic that will scan your OBC for codes, it will help immensely.
Search user jofj and see his SIG for info on your issue.
Sent from my SCH-R530M using Bimmer App
Bewahren Sie ihre ultimative fahrmaschine