Their live tone was so good in the late 80 s and 90 s . Sometimes I wonder if they put up with it for the convenience or if they really prefer it . <| sep |> I second all the answers and think those are all very real possibilities . however I find it really interesting your symptoms disappeared in a different environment . You could be having imflammatory allergic reactions to something you ' re exposed to at home , or maybe you ' re being exposed to mold or other toxins . I would maybe get allergy testing and a toxicology screen done as well . <| sep |> We ' re weird . It ' s OK to say it . We know . <| sep |> You might be able to narrow it down by unplugging the injector and see if it impacts the engine like it should . Or switch two and see if the problem follows the injector , you ' ll have to take off the plenum to do that tho . How did the plug look compared to the others when you changed them ?