Bad Torque converter or Catalytic converter?

Hey- I've done the research but can't seem to find solution that's fits the bill....
2003 PreRunner V6 175k miles

Problem: truck idles rough (sounds like it wants to die), and seems to shift late under acceleration. Engine sounds horrible at highway speeds. Truck has trouble getting over 65 mph without sounding like it wants to blow up. Rattles horrible at these speeds. Seems to get worse over past weeks.

What I've done: changed fuel filter, cleaned MAF sensor and throttle body, replaced spark plugs and wires, put two treatments of Techron treatment through.

No check engine light, but haven't checked for codes yet...so makes me think if it was a catalytic converter would be throwing a check engine light.

Any ideas?