So far my X has stood the test of time. The Dinan people I spoke with said that the transmission and diff are over built by BMW and can stand up to the addtional stress. Dinan also puts fairly mild parameters in when they tune a BMW. They are looking to keep the car capable as a daily driver and not put so much stress as to start breaking things and incurring costs warrantying stuff left and right.

My sense is that their is some room between the way my car is currently set up and the point at witch it would start breaking things like the Trany, diff & axles. The hard part, the fun part is finding that happy medium!

As far as the comment regarding "why not get a sports car?" I have had several as well as bikes including a GSXR 750RR (w/dry clutch, had it re-jetted, re-piped, added steering dampener, upgraded breaks, tires, blah, blah etc..) which I had a lot of fun riding, however my X5 is my daily driver and I love driving it during my day (I am in sales and I'm on the road often). Plus it is such a sleeper that know one is looking for a 456hp SUV in their rear view mirror!

If I can take something amazing like an X5 and make it better, then that's half the fun! I'd love to see just what is possible with this X5 platform! Who knows maybe 600hp & 500fpt?? I will keep you all posted.

Bigfish