My formula had bad injectors when I got it, causing the car to have a really bad idle. I picked up some used ford 19lb injectors (stock 5.0/4.6) for real cheap ($20) and they are good injectors. Buy yourself a gasket kit ($30-$40, comes with the injector orings) go slow and it's not a big deal you can get it done in a few hours just start early. It was my first time changing it and taking the whole tpi setup apart and I had them changed out pretty quick. You should be able to do the job for $50-$60 dollars.
-Jim
__________________
|