I have been taking all my BMWs to Sheni for over 25 years. I was very disappointed with the BMW dealer in Calgary at the time (T&T BMW) who continually mis-diagnosed a hesitation problem I was having with my 733. The dealer would guess at the problem, charge me and when it didn't work try their next guess (and yes they charged me). In frustration I tried Sheni and he found that the dealer had not correctly installed the distributor rotor after the last tune-up and that I didn't need the $1200 repair (which was the dealer's next guess). I've taken by cars there ever since.
Every time I take a car in they also inspect it and give me a "heads up" about repairs I may need in future. I have always found Sheni, Zuhair (his son) and Jozef at the front desk to be honest and pleasant to deal with. If you want the old parts returned just ask.
Sheni loves cars and knows his stuff. Give him a try.