Well, seeing how the car came from the factory with what I believe is a wax based anti corrosion protection sprayed all over the underside of the car I think I'll probably just leave it alone. I don't understand why they would apply it so unevenly though. I guess its better than having everything covered in that stuff though. Apparently this is a german car thing as I have not noticed it on other cars.
I pretty much maintain the cleanliness of these areas on a regular basis so each time I go to clean its really not that big of a chore. What I do is jack up the car and mix up some diswashing soap and water and also spray some Simple Green on the parts that I can't reach by hand. The areas that I can reach get scrubbed with a microfiber towel. I then use a pressure washer to rinse.
This time however, I didn't use dishwashing soap, simple green or a pressure washer. The wheelwells and undercarriage were still fairly clean since it's last detail, so all I did was spray a 1:1 mixture of Oil Eater and water and used a combination of a microfiber towel, paintbrush and toothbrush to scrub.
clnfrk- Lookin' great! I'm gonna take a wild guess and say that yours didn't have as much winter/salt exposure as mine did...your metal isn't nearly as pitted/corroded as mine. Heh heh, that great-looking rear diff housing makes me jealous!
Yeah, the stuff on the anti-swaybars is a wax-based undercoating. It'll clean off easily enough with solvent (less easily with degreasers as you probably found out) if you want to get it all off (I'd take it off places where it doesn't do any real good, but leave it on places where it'll serve a purpose). They spray it all over, better in some areas than in others. Cleaning it is a tricky trade-off IMO, too aggressively and you take it all off, not aggressively enough and there's still a lot of dirt stuck to it. If you have a steamer you can do a balaning act with that: heat it enough to soften it but not enough to melt it all off.
Thanks for posting this, I know *exactly* what it's like to do that job and it's not easy Nice to see somebody tackling this project and doing it so well.