Something else to consider is that the 'fun to drive' feeling comes from a well calibrated system which has a relatively high degree of torque on the low end with a good throttle response curve. You can get a relatively inexpensive tune and get a lot more pleasure out of the 'off the light' feeling than if you plop a whole lotta cash into a whole lotta system.

I drove the X5M and was prepared to drop a big chunk of cash on a brand new one but honestly, it was a major disappointment. I really expected to feel a MAJOR difference when driving it. It was such a disappointment, I told my husband not to bother coming out to check out the vehicle. It would have been a waste of his time. Immediately, I turned my focus to the 5.0i with the M Performance Package after driving the stock 5.0i without it which I was already impressed by compared to the X5M and that's what I decided on for my dd.

But when I jumped behind the wheel of my X5 5.0i with the Performance Package the day I picked it up, the amount of peppiness it had off the line brought a huge smile to my face. That's something the X5M was missing. And I really can't believe the X5M felt so heavy like it took a while before the big ponies kicked in. I wouldn't call it laggy. I'd simply call it uneventful. I'm SOOOOOO glad I didn't go for the big HP numbers. If I had gone sheerly by specs and ignored the torque / throttle response calibration, I would be disappointed in a $100K purchase as I type. But instead, I went with a highly optioned 5.0i and I have zero regrets. The 440hp and the tune of the M Performance Package gave me everything I was hoping for and then some.

Before you make your purchase of the Dinan package, see if you can find an X5M to test drive if you haven't driven one already and don't fall in love with the Dinan specs until you've convinced yourself that the mods are worth the money. You're buying yourself bragging rights and high performance but you could be disappointed in the lacking 'fun to drive' feeling if the calibration isn't set in a way that gives you the quickness off the get-go. Better yet, if you know someone who already has the Dinan upgrade on an equally equipped vehicle, maybe you can drive it to see for yourself?

By the way, on the mpg issue - I'm getting around 14.6 combined city / hwy with only 400 miles on the clock and I'll need to refuel tomorrow. I've been watching it improve from the initial 10mpg that I saw on the display when I picked up the vehicle last week. It's a trend in the right direction anyway. I'm hoping to get around 15.5 to 16 ultimately.