Speaking of an easy fix I had the same problem with my car my secondary valves were not opening (lack of acceleration passing 4000rpm). I found the 7 dollar plastic bushing missing and the metal rod that pulls open the secondary valves just hagging there. The Ford parts guy says those bushings always break. 98 SVT-93000 miles

'98 SVT #1838 of 6535, every mile's mine! That makes no one to blame but me.