My dealer is also a Dinan dealer so I've been considering this as well... it's not inexpensive but I guess it isn't bad relative to the torque/hp increase. Also considering the exhaust... I had a Dinan exhaust on my e39 M5 and I loved the sound. Anyone here heard the X5 exhaust yet?

It might seem silly but I can't imagine how much worse the gas mileage can get on this car... so far I'm averaging about 12 mpg and that's mostly commuting (half highway)