I've had horn issues ever since I first got my DSM. I don't know what it is to be honest but I've always had problems with mine. I replaced the horn itself and it worked for like a month and now it only works on and off. It seems like it works when it wants to. It seems like you've covered a lot...

have you thought about cutting two holes on your front bumper? I personally don't like the look of it but I know a lot of dsm'ers do the two nose-like holes to control heat issues. I can't give my two cents with the wrap because I haven't tried it out yet. Although I should look into it. Also...