Well, it realy depends on if you are also willing to buy a hand-held flash
tuner. Some do not require a tune but most do, and to get the best power you
would want one that does require the tune.
Some of the ones that do not require a tuner...
K&N, BBK, Granatelli Motorsports, C&L "street", AEM Brute Force, AFE stage
2, Airaid... just to name a few. Prices generally range from mid $200 to mid
$300 and horsepower gains run from 15 to mid 20.
The Granatelli and C&L will make the most horsepower, and are on the more
expensive end of the spectrum (naturally).
Do an internet search for any of these and that should help.
p.s. I have the Granatelli and am very pleased with it. I think I paid $349
for it.

I saw a "Shaker" hood scoop on a 2005 GT, just like the Mach 1.
It looked nice. I think the car had a decal or badge that said
something like
"Series One" but I have not been able to find anything on the net as
yet.

Reminded me a lot of my 1970 Mach.

rd

I have been looking at the Steeda CAI package as well as
americanmuscle.com and bamachips.com.  Sadly, the more I think about it,
the more I want a Kenne Bell, so I am just going to hold off on the
CAI/programmer kit for now.  I am starting to think that I shouldn't
have replaced my totaled vehicle with a Mustang GT because I feel the
desire and need to modify the Mustang, whereas I was content with my
bone stock 2007 V6 6MT Honda Accord Sedan.....