EHA was replaced before, it is not original. I have 2 to 3 parts each of igntion/tune up/fuel related components and no matter which I switch around the same issue is still present. I went to my muffler guy and he too said that the cat is fine and that I have a misfire under load at low rpm, he though it was maybe a vacuum leak. I have a vacuum tester and was checking each line for a leak, the only one I found was to a red/light blue striped line on the driver side behind the firewall right above the brake booster. I traced the line down into the front passenger wheel well behind the plastic panel. I removed the panel and the line terminates into a black plastic bouy type ball that doesn't appear to connect to anything else.Its attached to the wheel well and has nothing else connected to it other than the vac line coming from it. I also put another brand new Bosch distributor cap on today as well (because I ended up checking and rechecking my ignition components I ended up breaking the carbon top in the center) This is got to be the most frustrating thing ever. Even the electrical fire I had I was able to replace the wire harness in 8 hours. But this I have been dealing with for a couple weeks now.

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1990 190E 3.0L