Last year, before I even received my car, I had ordered all the upgrades I wanted for the beast (H&R springs, 20" BBS RS-GTs, CF wheel, pedals, Hartge front lip, etc). By 300 miles, I had them all installed. (Finally, my new beast w/mods, inc. Brembo!
After half a year, I've grown to love some of them, and wished I hadn't done others. Follows are a number of highly subjective observations that are mostly personal to me.
The first thing to go was the front lip. Hit curbs all the time, and a little to "boy-racer" for me in Silverstone II. I love the RS-GTs, but when running the 13mm/10mm spacer combo, no matter how much material I took off the rear inside wheel well, with 4 people, in a turn, with any bumps, the rear wheels would scrape. Also, I felt the H&R springs made the car look a little too "slammed", and I also felt ride quality was a little too choppy.
So, I just had Dinan install the new diff and exhaust, and decided to change out the H&Rs for the Dinan Stage II. I also put the 10mm spacer from the rear on the front, and ran no spacers on the rear.
What a difference! The car raised about 5/8" in the front, and about 3/8" in the rear. The ride has improved tremendously! I like the look much better than with the H&Rs. It is aggressive, but not overly dropped. With the sway bars, the car also feels much more "tossable". With the rear spacers gone, the occasional rubbing is gone too.
I'll add to the praise everyone has heaped on the diff change. It truly is like P600!
On to the Dinan exhaust. I use my car for business sometimes, so I was concerned about too much noise in the cabin. I have Eisenmann Race on my Z8, and was not looking for that much noise. The Dinan M5 exhaust is perfect for me. It definitely has a deeper growl at idle, and when you really punch it, it gets loud. However, for everyday cruising, even at highway speeds, it is just fine. You also can't beat the look of four 3" pipes out the back.
If Brembo ever ships the rear BBK for the M5, that will be my next install. Every two weeks, it slips two weeks!
Finally, for those of you waiting on the new Dinan software... I saw on another post that the release was anytime now. After talking with Dinan, it seems that they order the ROMs programmed once a month, for that months shipments. They just ordered all the ROMs for March, and there are none for the M5, which my guy told me mean't that there wouldn't be any available until the April order is received, which he felt would be around 4/10. (For what its worth)