Joined: Mar 2008
Location: Lawrenceville, GA
If you want better acceleration, a rear end gear upgrade will give the best seat of the pants feel and knock a few tenths from your quarter mile times when paired with good tires. If you have 3.31s in the car, going to a 3.90 would be a nice upgrade. If you don't do a lot of highway driving, I would even consider 4.10s as they'll get the car moving even better.
If you insist on the intake & tune route, getting a tuner from Ebay is fine. You just need to make sure the tuner is unlocked AND unmarried as the custom tune files are specific to each car. If the previous owner did not unmarry the device from his car, you will not be able to use it and the cost to get that restored from SCT is $150. Oh and stick with a SCT X3, X4 or Bama tuner. Most tuners prefer SCT devices.
There are cheap intakes that don't require a tune but they don't yield much power, if at all. To stay within budget your best bet is to look around the forums and find a used one. I'm seeing lots of different brand name intakes in the $150 range.
2007 Mustang GT/CS coupe
Procharged--cammed--Kurgan tuned--coilover suspension