I dont necessarily think it is your only problem but the plugs you have in there are the large electrode model (0 on the end, 9dc0). I dont know your car but for mine (84 380sl) a w9dc0 spark plug caused a number of problems with the car, mainly a jolting hard miss at idle. I pulled them out and put w9dc in there (versus w9dc0) and the problem instantly went away. To verify I put them back in and problem came back. Even used multiple different sets of the. It was a real problem. For cleaning your fuel system, I highly recommend Chevron Techron, the big bottle. Put it in there on an empty tank, fill up, drive hard. For what it is worth (probably not much) my first reaction to your problem was bad fuel distributor (I think your car has one like mine). A rebuilt distributor for a 380sl not rebuilt by bosch (they are expensive) is $500, mine works great. It is a relatively easy thing to change on my car. Be sure to replace all rubber