Congrats on your new purchase! You won't believe the power in the 550...I've had my CPO 2007 about a month now (10K miles on the odo!) I upgraded from an 04 545 and absolutely LOVE the 550.
I had an 07 335 cabrio and how I miss it...but I also had a little one, so it had to go. I found the 335 had great takeoff, but the turbo lag hurt. the 4.8L in the 550 is a monster- I call mine 'The Beast'.
Good Luck with it!
