Help Me Decide - Dinan Upgrade on New X5 50i

[Btcus]

After much research and test driving I will be taking delivery of the X5 50i below and would appreciate some perspective on the differences between the stock 50i and upgrading to the dinan stage 4 with High Performance Air to Water Intercoolers (skipping stage 3 exhaust hardware upgrade. This will be my daily driver @ 10k miles per year. I plan on keeping the X5 for at least 5 years.

Build:

Silver Metallic
Black Perf Nevada Leather
Dark Bamboo
Luxury Seating Package
Premium Package 2
Premium Sound Package
Sports Activity Package
20" Wheels
Adaptive Drive
Active Steering
BMW apps
BMW assist

Here are 6 questions that I wanted to ask the members that have upgraded this x5 50i Engine with the Dinan Stage 2 (and above) software. (Thanks for bearing with my OCD and thanks for the help in advance)

1). I am concerned with the gas mileage as I have read about substantial decreased in MPG after upgrade. What differences, if any, did you experience with your gas mileage after the upgrade?

2) I am concerned that the upgrade will result in some frustrating side effects around the daily drivability. Did you experience the transmission acting "jittery" or "lunging" in bumper to bumper traffic? Or when needing to give very little throttle to move short distances? (Pulling into the driveway or parallel parking?)

3) I'm considering taking advantage of the 15% discount on parts being offered for the software upgrade and Intercoolers. Has anyone done better than the 15%? (I plan on having the upgrade done at the corporate headquarters in Morgan Hill)

4) I am concerned that 'skipping' the stage 3 exhaust hardware upgrade and jumping directly into the Intercoolers upgrade (stage 4) will result in poorer performance as it relates to the smoothness of the transmission and power flow. I have read this on a few posts. Is this correct?

5) anyone wish they "had not" purchased the upgrade after instal? Why?

6) any reason I will regret the upgrade given how new the car is? (Would you recommend enjoying the "stock versio" for a while.

Thank you!

Brian