I purchased a 2016 M235i cabriolet in February 2017 with 9,000 mile on it. It was a cpo and now has 37,000 plus mile on it -- love driving it. Lately I have been considering having my dealer install a Dinantronics Performance Tuner Stage 1 kit on it. Based on Dinan's literature it is my understanding that it adds 40 bhp and does not affect drivability or mpg. Do you have or do you know any one who has installed and has real world experience with it. How accurate are Dinan's claims?