Originally Posted by pyceasyas123
I have JB4. It will void your warranty if the dealer knows about it...but JB4 is really easy to install/un-install. I used JB3 for 3 years on my old e90 and I've been using JB4 for a while now. I don't think that warranty should be a huge concern...you can always read and delete codes and un-install it before going to the dealer.
What kind of gains did you see from it?