How many miles on this 05'?
Could be several things contributing to your mpg drop.
If your fuel filter was clogged.
Could be your emissions system having something not working(egr,cat covrt,O2 sensors).
Even the plugs and wires could be the problem.
If you are referring to the 03-05' GA Flat wings I think they are from the Aleros. As far as Hoods, try
PFYC .
You migth be able to find one at a local stealership for about the same price, and would probly save on shipping.