I just installed the BMW Performance Carbon Fiber front underspoiler on my E92 M Sport LCI. Installation was pretty easy, took about an hour with a drill and hex wrench. Fitment is 100% perfect, as you would expect from an OEM part. It is also pure CF, light as a feather. This probably isn't more than a couple ounces, if that. It's a beautifully manufactured product.
Thanks Jason & Evan @ Tischer for ensuring the product arrived unscathed!
I am writing a DIY. I put the car up on a 2x4 and put it on my front driveway lip, plenty of clearance. Or you can jack the car up.
DIY HERE: http://www.e90post.com/forums/showthread.php?p=10435521