By the way, it's Western Motor Sports, not Westin.
Anyway, I had the WMS Ram Air on my 2005 GT for about 6 months. The install wasn't too bad. It only took me about 3 hours. The performance was good, especially after I had it custom tuned by Brent at Brenspeed.com. Ran 289 RWHP and 307 RWTQ.
All that said, I would NOT go with it again. With the repositioning of the coolant tank, you have to cut a couple of hoses, in addition to lengthening some of the wires for the mass air module. These changes make it very impractical to ever put the car back to stock. You may think you won't need to, but you'll get pretty nervous if you ever have to take you car in for warranty work, and the dealer gives you heartache over your aftermarket parts. Not to mention if you ever go to trade in the car. Dealers don't like to see major mods to stock. It can hurt the resale.
I now have a 2006 GT and decided to go with the C&L CAI and Brenspeed 93 tune. I am thoroughly pleased with the C&L intake, and the install only took me about 30 minutes. And, the best part, if I ever need to go back to stock it will only take me about 30 minutes.
Just something to think about.
Good luck.