Mine does a similar thing but in third and around 2.8k rpm. It only does in third and no other gear, and not always. I would describe it more like bogging down.... when applying full throttle at about 2k rpm in 3rd gear, goes nicely up about 2.8k rpm when it feels like it's losing power for a second or so.
11 Audi RS5 Misano Red
08 E92 M3 Jerez Black 6MT--sold
08 E92 335i 6MT traded in for M3