Slant won't drive over 25mph without cutting out

Is it possible that when you went to work it was in low humidity conditions, but coming home it was raining (or otherwise high humidity conditions)? Water conducts electricity (at least water with "stuff" in it like rain water or water splashed up from the road). You may have a fuel system issue, but that electrical arcing at the coil delineates a point of first attack.

For tune-up parts, I have had excellent results with NAPA Belden and Blue Streak cap & rotors. They use brass terminals; much more durable than the aluminum terminals found on most (even OEM) caps. Second, ignition wires leak. The best wires I've found are Granatelli solid core wires. They use a ferrite ring that suppresses EMI. I use them on our ECU controlled Grand Cherokee.

Chryco used Champion Spark Plugs from the factory. Therefore, there are diehards that swear by them. Understand, today's Champion company is not the same as it was 40 or 60 years ago. I swear by Pulstar Spark Plugs, as they incorporate a "peaking capacitor" in the plug to generate a mild plasma spark.

I also found a web site with an informative dissertation on Ignition Systems that I believe may be of use. Like I said, you may have fuel system issues, but arcing coils would get my attention first.