I have been pretty much on the boat to buying the Stage 0 from Vishnu. After extensive reading on e90forum.com It has been fascinating and very encouraging. Until the nagging warranty issue was brought to light…. I had gone to Sterling BMW and had a discussion with a top mechanic. He hadn't heard anything about the Xede. When I told him, he was seriously puzzled about how the engineers at BMW would NOT find traces of something that boosted the HP 55 and above. This guy says main line techs may not see it, but when a serious warranty issue takes place, the engineers have a totally different laptop that they can see everything, for 6 months or more back. Hard shifts, the exact rpm between shifts day by day, shift, by shift, everything.
Then I saw this 3 days later ion e90forum.

“Taken from a BMW dealership employee...

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I just had a conversation with the BMW Field Engineer assigned to my dealership regarding 335s. It's been known for a long time that when a technician connects diagnostic equipment to a vehicle, a report is generated that contains the 'vehicle order' and each night all of the day's reports are transmitted to BMW. The vehicle order is contains all of the information about vehicle control units including their hardware version and all of the binary coding for them.
BMW has developed a tool that compares the vehicle order of each 335 to the known vehicle order at time of manufacture. Any deviations in the binary coding of the DME automatically alert engineers that the code requires further inspection. If the code related to boost has been altered to create a high-boost scenario, the engine warranty is immediately terminated.
To date, they have terminated 54 warranties.
MORE IMPORTANTLY IS THIS POST: A good rule of thumb is if you are leasing a car...don't mod it. The car doesn't belong to you. If you void the warranty, then you are in breach of your lease contract, which is then terminated. It happened to my friend with a 5.0 mustang who made the motor go Kaboom with a hefty dose of nitrous. He was responsible for the cost of the engine replacement. He had to turn the car in and was responsible for the lease payoff minus the realized value of the car, which was considered to be significantly less than market value." "It's a violation of the lease agreement and I think they force you to buy it at lease end (rather than accept it back)."

Many of you will repeat what's already been said, “you pay to play, if it worries you, don't do it” etc. But I for one didn't know the extent of the danger of a mod like that, because I've never had a brand new car I did something to (modded). I hope this info was helpful to some. It sure opened my eyeballs. I’m not touching so much as a muffler on this leased 335i. I guess I agree with some posters, if you want an M3 or M5, then buy one in the first place.

2007 335i Sedan
2004 King Ranch F250