looking good on the floor mats I'm surprised you didn't use the detailers trick. which is to put it in the washing machine. i do that with the floor mats on the 330i and each time they come out looking brand new.

regarding the engine detailing. i wouldn't use simple green unless you have serious grease build up. if it's just dusty all you need to do is wet it down and use a nylon brush, then rinse and then go over it with a terry cloth. follow up with 303 and it'll look brand new. i did this with wills integra. i have before and after pics, you'd be surprised what a little bit of water and elbow grease will do... that and 303