Don't kill me for digging up an old thread, but whoever said these (2) different covers are totally interchangeable was/is wrong.
I have a 1-piece & a 2-piece, and they have different mounting points.
I will get hammered for this, but I actually wanted to go to the 1-piece to cover the bolts on the top of the intake. Being a daily driver here in MI, and starting to age, there seems to be some point where water gets on top of the intake and pools on the top of the bolt heads for the intake. Because of that, I don't want to deal with corrosion there, and bought the 1-piece to just cover it all up & protect them. I mean, it's just a base model, a daily driver, and nearing 200k. At this point, I'm more worried about the corrosion than I am the look of the 2-piece.
The mounting points are different, and the 2-piece only secures at the end closest to the throttle body.
Wasted money thanks to this thread lol! It's been 8 years, but maybe it will help someone else.