03 tacoma d-cab 4x4 hard jolts

So I've scoured the internet for comparable situations to mine and see if there were any clear cut remedies. The situation is on the freeway at about 50mph all the way up to roughly 60mph at about 1700-2100 rpms the truck will experience a harsh shutter or jolt for a few times while accelerating until I pass roughly 60mph. I had the CEL on due to the cat converter (P0420 code), did the URD O2 simulator installed to shut off the CEL. From what I've gathered through internet searches, I believe I narrowed it down to these possibilities:
- unbalanced wheels
- spark plugs and wires
- clogged cat converter
- bad torque converter

I looked at my driveline and nothing seems to be out of whack. The U joints seem fine, transmission shifts fine, shifts into second at a higher rpm than normal, rear axle seems fine along with rear suspension. Checked transmission fluid and seems dark shade of red. 2003 Tacoma D-Cab 4x4 w/ 113k miles. Thanks for any help gang!