Ok well i am definitely leaning towards the catalytic converter being plugged now. Havent actually removed it to inspect visually yet but I loosened the bolts in front of the cat to create a 1/4 inch gap or so between the flanges, then took it for a test drive all the way to having the engine hot about 15 minutes or so.
While the issue isn't 100% eliminated by doing this, it is NOTICABLY improved. Particularly accelerating from a stop even when hot, and perhaps a smoother idle. Even the higher range speed acceleration is seemingly improved a bit.
Not a concrete proof with only one test drive so far, but definitely something.
Going to look into cat work this weekend I think.
