what do you think of this?

http://cgi.ebay.com/ebaymotors/MAC-R...QQcmdZViewItem

 

Stay away from such things. Every Mustang is unique. Finish your mods and then get a custom tune from someone like Brenspeed.com who supplies a custom tune for every customer. The best device to add HP to a Mustang in my opinion is an adjustable timing adjuster as sold by Brenspeed and made by Steeda. I have one and with 93 octane I was running an extra 6* base timing which would then add 6* throughout the rpm range. Better performance and better gas mileage though I would suggest only going 14* instead of the 16* I am running. Once you get a custom tune you will not need the timing adjuster. I may sell mine as today I ordered a Brenspeed tune in an SCT tuner. An ebay tune made for every car will be very conservative if it offers much at all. mark