Need more info. Your 535 model year, JB version (stage 1 or stage 2) and map # for starters. Also, when the stutter happens, is the oil temp guage moved from it's lowest position yet?
The N55 JB4 Stage 2 shouldn't raise boost until the oil temp guage begins to move. So if you're problem is happening before that, you're still at stock boost and it may not be a JB4 issue.
2014 Audi S5 DSG
2011 335xi Sedan (retired)
2008 335xi Sedan (retired)