dafairm

I have a 98 cobra with a K&N Air Charger. The car idled high, until I put in the air charger. This solved the problem for about a month. Now I've been idling high (1400-1800)all over again. Also, when this started I noticed that the car is sputtering in 3rd at about 100 mph. The "check engine" light comes on when I drive hard on the freeway too. Took the car in to ford and they said it's a "secondary" fuel injector problem. $700!! I don't mind, but I want a second opinion? Can anyone help?