FWIW. I got a remanned dizzy and it didn't last a week..
Where is your timing set?
What engine mods do you have.
Fox's have problems with the ICM/TFI module not sn's. I'm not saying it's not, just that it's unlikely.
Quite honestly I don't think you have an ignition module issue. Idle surge is definitely not related to the TFI module nor the dimming of lights. As the causes of an idle surge have many possible fixes you really need to check for trouble codes (DTCs) but first check for a vacuum leak. The dimming of the lights may be an alternator, battery or grounding issue. You need to do some diagnostic sleuthing.
since you have a CAI, try cleaning the MAF and air temp sensor.
the 5.0 are getting older and were seeing more and more TPS problems. I had a hanging idle and a dead spot in the TPS was the cause.
Stock timing is 10*btdc (spout out) I'm running 12*.