SD works when properly tuned. Though the factory Ford ECMs are known to be persnickety when it comes to idle control, particularly in regards to cams. Most of the aftermarket setups overcome it by having an algorithm that forces the fuel control to switch to alpha-n under a set rpm. So say, under 1,500rpm it stops being SD(looks at MAP, TP and RPM) and becomes alpha-n(looks only at rpm and TP, and ignores MAP).

And if worse comes to worse, FAST sells a stand alone ECM that you can plug directly into the factory harness for various vehicles. Basically an ECM upgrade from the stock computer. Or you could go with Megasquirt, which is more of a project than a system.