Fixed! Well, it wasn't the cat. Or the crank sensor. Or the ignition module. This week when my dad was driving it, it melted a fuel pump fuse. A problem I was having before & I replaced the pump & hadn't had the problem again. Long story short, the socket that the fuse plugs into was loose on the top side so as the engine compartment changed temperature it loosened its grip on the fuse causing arcing, melting one side of the fuse. And evidently causing the lack of power issue. Basically, fuel starvation with the fuel pump not getting full power. So, my original fuel pump was probably ok too... I hate electrical problems!