Well, it depends on what you call cheap....
An intake is probably you best, cheap mod that you can do with a noticable difference.. right now I think the BAT is the best one for the Duratec,.. correct me if Im wrong, but ive heard nothing but good things.. but if you really love your car as much as me...invest into HPP's(chris hightower) Turbo for the Duratec....
http://hightowerperformance.com/ there is his website...
