Can't say I've noticed anything like you mention. Although I've only had my E90 for a couple months. I've just recently dialed it in with the correct JB4 map and E85 ratio. I usually flog it through a few gears at least once a day and it seems to be fairly consistent... FAST!
2008 E90 TiAg w/ Sport Package
JB4/BMS DCI/RL DPs/Black Kidneys/VMR 710 (Gunmetal)/Blacklines Tailight