I am in Florida and have a 1990 190E 2.6. I have had the car for about a year and it has 206,000 miles on it. Within the last few days when you mash the gas the car hesitates, sputters, backfires and then eventually it will stall. If you let up on the gas and push it easy it will gradually build up and go just fine, but once you slow down it does it all over again. This problem only happens when the car is at temperature. Before this happened the car would not start all the time. I pulled the plugs and they were gunked up with ash, so I replaced them. I also put fuel injector cleaner with 93 octane in it. Now the car starts fine, but I have the new problem that I just mentioned above. Any ideas what the problem could be?

from the sound of it the problem could be four fold.

1.the fuel distributor could be going bad .
2. the fuel regulator could be going bad
3. u have a leak somewhere in the vacuum system
4.check for gas leaks around the fuel distributor

any of these four things could easliy cause the problem

number one is my best guess.....try to find a used on in a junk yard this item is very expensive new.