on my 79 450SLC, and the improvment in idle was the most noticeable. BUT you have to be careful using this stuff, TBs are no like carbs, a lot more senitive to damage. Also, you need to me very careful not to spray too much on the TB sensors. I pressed the TB plate down carefull and spray iniside and around the TB plate and gently pushed it up and down to make sure it was free and move freely. Then as instructed on the can I carefully wiped off as much of the cleaner as I could, checked to make sure everything was connected. I also sprayed the accelerator linkage with engine cleaner and used a wipe cloth to wipe it off and a dry cloth to dry. then I made sure everything was tight on the linkage and the lubricated it with Hydraulic oil all the way up to were it goes into the fire wall, and down to the tranny as far as I could. After that I lubicated the pedal linkage, inside the car. These are all recommended by Mercedes as service procedures. But there could be another problem. You didn't say if you have a automatic. On my 450 there was a recall in 1980 which required the shifter linkage bushing to be changed to a metal bushings. I could have had Mercedes do it for free, but I bought the metal bushing and installed, 1/2 hour job. Before that the tranny would't go into gear, and I had to move the leve back and forth and got a considerable jerk in neutral. Since I installed the new bushing the tranny shift from P to L very softly and goes into gear immdiately. I have 115K miles on this Mercedes. So what is the point? look to the shifter linkage and the accelerator linkage that might be the problem. Also, cleaning the TB is somehting I would do, as I know what can and can't happen, but this is done for carbon buildup cleaning the linkages would probably be better. Also, if you don't tackle the TB cleaner, put the higest octane available, around here 93 Shell or 92 Mobil is available, and run the car down to as empty as you feel comfortable with and then refill it a couple of times and drive it if you can on the highway as fast as legally allowed, this does a lot for carbon. Also, as gas and or diesel is so pricey, try a bottle of exp4 gas additive. go to
www.exp4additives.com. It was tested on a show on SPEED TV and it added 5 hp that was lost due to age and mileage. I just received a can and put it in the tank when it was on Reserve, drove to the station and filled up. It is know a half tank down and the engines runs better and better. and also gas mileage has improved. It is available for gas and diesel. I also have a 99 C280 and I really don't drive a lot, as I am partially handicapped. The gas mileage dropped down into the mid teens, after pouring this stuff and running a tankful of gas I am back up to the low 20' mph on the highway.