like the rest said, it's a small magnet inside your distributor. When it goes, you'll notice random, but worsening stall issues, starting problems, etc.
2 fixes, replace dizzy, or rebuild it. I rebuit mine when it went, took me an hour, a vice, a hammer and a busted finger, IIRC
Just buy a nice MSD dizzy and don't worry about it.
Ford makes awesome distributors. Much better then the MSD ones. I have an extra Ford Motor sport dizzy for a 351 just in case the remanufactured NAPA one decided to go at anytime.
You hear, you heard blah blah blah, i had mine for over 3 years, the whole complete MSD system, Not a hick up, Install it correctly and you will be fine.
But if i were you i'd go back to fox body, I know i will own another fox pretty soon, I regret so much selling my 91. Dam it!
But for 94-95 mustangs...Who cares if they have body flexes and balancer go out and blah blah blah, you gonna upgrade and eventually go all aftermarket anyways...
When i bought my gt i promised myself i would do exhaust, body kit, lowering springs and that's it, Leave everything else stock to be more reliable. but look where i am now, it's disgusting
My MSD 6AL ignition box died on me this past spring. Not sure how old it was b/c it was on the car when I got it but still. MSD used to be top notch but their quality control has become suspect over the past few years for the stuff they are putting out now. Lots of other companies out there that make good dizzy's. As I said when it comes to that you cant beat the ford ones.