No emissions here, but I hesitate to gut the cat or put a pipe section in it. Do you guys really think it might be the cat? If it was partially plugged, wouldn't I see sluggish performance and/or maybe increased engine temps? I had one plug in the past and the engine went into the red pretty quick...

I'll keep trying things - I hope to get to the bottom of it because, after all of this work, the vehicle will go to my brother who really needs it. And, he's not too mechanically inclined, so I'd like it to be as trouble free for him as possible.

I appreciate all the ideas and keep them coming! Thanks!