I use Gunk spray on engine decreaser in a can for really tough stuff. Haven't needed it yet on my '04, but it did wonders on my old foxbody. Simple green works just as well if not better.. I just happen to have like 3 extra cans of Gunk in my closet.
I use CD2 detailer to make it all shiny and wet looking.. stays that way for a month or more usually.
Lastly, I use a steam cleaner I bought from Walmart's website (a Eureka something or other, big yellow one) to clean the wiring harnesses, nooks & crannies, etc.