That is very weird that you did not notice a difference with the tune. I have had the BMS JB4 for a while and noticed an increase going from Stage 1 to Stage 2, then the software update with Map 5 introduced, then running E85 (3 gallons) and now with the ISO tune.
I can only give positive reviews of Terry at BMS and the products that he has provided for the N55. Sorry to hear this and hope that you enjoy your 335is. That is a purdy car!