Auto Enginuity
Auto Enginuity offers good cost effective diagnostics for the professional as well as the DIY'er. If you have 4 Fords just get the Ford kit and use your own laptop. It's good for everything that you would normally have to have the dealer do. It'll pay for itself the first time you avoid going to the dealership too. Their tech support is very good too, very helpful and friendly. I have the Ford, GM, BMW kit and it's been very helpful in diagnosing any problem that pops up. Fortunately not many have come up because I stay on top of the maintenance. But the software may help you catch something early before it becomes a big issue. Like a bad plug, or coil or some other switch that's intermittent.
http://www.autoenginuity.com/
-Mike

