Well, not only did I figure out a way to clean the pipes, this morning I discovered where the schmutz came from--I now have melted car cover on both sides. I was able to scrape most of it off, but will be back at it tonight with steel wool and heat.
Does anyone have a recommendation for a decent car cover that has heat-resistant material on the rocker panel areas? I called California Car Cover and they will make a cover, send it to me to mark-up, then I need to send it back to them to add the heat-resistant material. Seems like a lot of work, especially when Harley Davidson covers come with heat-resistant material in the pipe area.