I never worked on the EHA and am not familiar with it's function.
I just did a quick search and saw that it is fuel related so I would definately ask the forum if the EHA could cause your symptoms.
Possibly start a new thread and do a search to see what you can find out.
If its disconnected then I'd say that you have an excellent starting point for troubleshooting the problem.
1993 190E 2.3
2000 Toyota 4x4 Tundra