+1 on the Steeda, its a quality piece. I ran it before I went the procharger route. Not sure about the gains but it looks nice and has a good sound to it like ChiZ said. IF you're concerned about the hood vents letting water in JLT sells a piece of foam that will block off the part of the hood vent that is over the CAI.
2014 Mustang GT 6R80, Procharger Stage 2 D1SC, BBK 85mm TB, Boss IM, Sai Li fuel system. Circle D 3C, 1-7/8" Kooks Long Tubes w/Offroad X Pipe, Lethal Over-Axle Pipes, Corsa Quad Axle-Back, Eibach Pro System Plus, BMR K member, Shaftmasters DS, Forgestar CF-5 Wheels and Nitto NT05 tires. Lund Tuned
Lots of suspension goodies and some other stuff I can't remember.