So, 7 years and 3 days after this:
It's cleaning time again!
I set the car on some truck jackstands to get it in the air as high as possible and then soaked the underside with purple stuff cleaner diluted with 2/3 water.
It then donned the Tyvex suit and face shield (much better then the raincoat I wore back in 2005). I then spent the next 8 hours pressure washing the underside. I think the key to getting the undercoating off this time was using hot water. I ran a heavy duty garden hose through the window and hooked it to the washing machine hot water feed. It worked great!
Half way through the day I ended up pulling the aftermarket exhaust to get a better angle on the floor boards.
