Engine misfiring on Bank 1 possibly due to timing problem. Could be timing guild

Dear Zippi 1, I have been working on the BMW for 7 Months now and had Reset Adaptations with no changes in the motor. I took it to a BMW shop and they put it in a diagnostic machine and tried a couple changes in the motor and they could not change the conditions; so they said that it must be a BROKEN TIMING CHAIN RAIL GUILD, or VANOS GEAR is bad, or just maybe the TENSIONER is bad. The car idles smooth and even when driving, but, you can't push on the gas, as it will want to stall out or the engine shakes, it will get up to speed eventually and has gone up to 80 mph. The Bank 1 continues to miss on 2 pistons and the car will get you around town, it just takes long to get up to speed. I have my doubts that it is the RAIL GUILD that is broken. The shop would not tear open the engine unless I cough up $ 4,000.00 so I took my car back home. Hope this helps you. Sincerely, Ron