DIS module Problems

Haven't posted in about 6-7 months here but, need help.

Have 2.3L Mustang 92 double spark ignition. Initial symptoms, modual sent bad tach signal (tach read half od what it should). Engine ran fine, slightly rough idle. Replaced modual (used) same problem, replaced with another modual (used) worked great for about a month, started having intermittent missing on one cylinder, then constant missing, in each case accompanied by the same bad tach signal. replaced with another used DIS modual (I bought 2 at the junk yard) ran fine for a day started having the miss again, this time almost immediately constant, same bad tac signal. Called mechanic, he says that a bad pack or spark plug wires can blow the moduals, replaced plug wires, had heavy corrosion on several of them. didn't have any other moduals, put the one I had (bad tach signal, runs good) back on, car has been running just fine, with bad tach signal. Could I still have a bad coil? Any info on the modual would help, I understand the function, knowing why the plug wires can blow the IC in the modual would help. A question for some pretty indept people I know but I think I'll ask before I send it off to the mechanic.

Well the heat conduction is definetly not the problem, the chip inside is not big enough to burn its self out. Chances are that the intake manifold gets hotter than the chip ever would. Still might be important but heat conduction wouldn't explain why one modual lasted a month and one only lasted a day. I could use a pin out on the actual modual, if anyone knows what pin is what. At least then I could take it to school and put a signal on it and see which output pin is sending a bad signal. would a bad coil pack still produce a spark?

I think that having the bad plug wires probably fryed the last two I put on. I figure it that weren't the problem the car would most likely make the other one I put on go out too.