Igniton Coil Problems?

I have a 2000 Silverado Z71 with the 5.3L vortec. About a month ago, the truck started having hesitation problems whenever I would try to start quickly, and having acceleration problems in general beyond first gear, and the mileage also dropped significantly.
I had the injectors cleaned, replaced the spark plugs and wires, replaced the fuel filter, all to no avail; the problems have continually gotten worse.
After viewing another thread which suggested looking at the running engine in the dark to check for sparking through the cables to the block. I discovered that at that time three of the igniton coils were sparking between the plastic canisters and the metal part of the coil. I ordered replacements, and then this morning went to check again to make sure I got the right ones, and six were doing it. The sparking is intermittant, but it happens quite frequently. The truck had not been driven since I first found the sparking problem.
Has anyone else had this problem? Can anyone explain to me why six would go bad so quickly, and why the truck still runs and gives no service codes? Am I barking up the wrong tree? Help! These coils are expensive, and I don't want to replace them if they are not the real problem!

Thanks,

Jon

you might try covering them to see if they stop, but i dont know what you could use that would stop the arching. try tape just a thought might be a temp fix.

Unscrew your O2 sensors before the catalytic convertor its gonna be loud but start it up and see if they are still arching if not you have a pair of plugged cats...I had the same prob with my 99' missing and arching all over the damn place and unscrewed the O2 sensors and it leveled off and didnt misfire or anything. What happened was exxhaust was staying in the chamber cuz it had no where to go which casued the coils all to misfire? dont understand it really but it didhope this helps you.

What do you do about clogged cats? How do you prevent it?