Recently I have been having a lot of surging/misfiring issues so I stopped using the octane booster and all went back to normal. Had spark plugs checked and they were fouled because of the octane booster i was using. Was fine initially but I guess the build up started causing these misfiring issues. Car runs perfect now. No more octane boosters for me.
2012 BMW 640i (AC Schnitzer Package)
2011 Mercedes E250
2007 Ford Mondeo
"Age is but a statistic that has no relevance to enjoyment of horsepower"