Well, here's one on Gunk:

"Gunk makes a citrus cleaner which I hear is pretty good. Myself, I have mostly been using Simple Green and plain old car soap. But I bought a CD2 engine detailing kit and will be trying it out soon."

"I think the general consensus is that Simple Green left on aluminum for long periods of time will stain,"
"I stay away from simple green after using it on my engine once. It turned all of my hoses grey/green and I had to use a rubber dressing to get them back to black. I have heard that citrus degreasers will not do this."

Simple Green = NO

Another thing somebody suggested is to go to your local spray and wash (self wash) and use their engine cleaner setting. Remember to cover electrical things (alternator and coil pack--err, dist. in your case with aluminum foil or seran wrap). Oh, and don't leave the seran wrap on when you drive away of course.

After winter this year I used the local self-wash with the engine cleaner setting and it did work pretty well.