got turbo 4 wks ago surging and jerking problems started on 3rd day I had dealership thought bad gas from corp. They drained tank and told to run Shell v-power 93 octain have done so but problem has got worse including black smoke pouring out exhaust tips , now they have replaced plugs w/ only 650 miles on them w/ severe carbon build up and bad spark knock and the whole time no engine codes going off , drained tank again and had me put 87 oct. back in and they installed a flight data recorder in the car so every time it surges and bucks I push a button to record last 10 min. of engine functions. I think they