If I go to a "do it yourself" carwash, aka presure washer and spray the engine from under the car (with the plastic sheld removed), would I damage anything? I think it would be ok, but it's usually advised not to spray an engine and the tt has a sheild to protect it. Are there any sensitive electronic sensors down there?

 

Nope. Just get some Simple Green and spray around under there to loosen up the grime and blast away.

 

Plastic shield is more of an aero component than a guard.