Vibration when accelerating 20+ mph

My truck seems to be falling apart like a Lego set right now so I need some help. This will be a long post since I want to give as much info as possible.

I’ve got a 1998, 4wd SR5 automatic transmission that’s had a vibration issue for a long time but seems to be getting worse. It kicks in at about 20mph, settles a bit at 60, then picks up again from there. The vibration starts as soon as I depress the gas petal and you can feel an initial thud, almost like it’s engaging, but it stops as soon as you let go of the gas. It’s pretty loud too, at first I thought it was rough tires since I’d never rotated them but after I had that done I noticed how it reacts to the throttle.

A little history:
It’s had a P0171 code (fuel system too lean bank 1) on for about 3 years now. Not too long ago I replaced all 6 injectors with brand new Toyota ones, and when I went out for a drive it had zero acceleration when stopped. It would stall out and sputter, then take off like normal. The P0171 code also turned into a P0172 code (fuel system too rich bank 1.) Gas mileage went down the gutter. After changing a ton of parts I finally put the old injectors back in there and it ran perfectly fine, (code back to P0171), and after some seafoam treatment the CEL when off. But now it just comes on and off at random.
It also makes a clanking noise whenever I put it in drive. It’s always done this and I’ve read it’s normal, but it seems to have gotten more aggressive. And I don’t know if it’s related, but just today it started to misfire on me in cylinder 6.

The last person I took the truck too before I put the old injectors back in said my ecu was no good, that it was telling the fuel pump to stay on high. I dismissed it after I got it running back to normal, but now I’m starting to wonder again since the CEL keeps blinking on and off.

Anyways, I’m mainly looking for a solution to the vibration, but wanted to throw any information out there I could that might be useful. Sorry for the long post, I hope someone could take the time to read it and help me out.

 

Might be a Failing torque converter ?

 

That’s what someone else said as well, might get that checked out. Cylinder 5 started misfiring today too. More fuel to the fire

 

Whoever said these trucks are easy to work on makes me wonder. I suppose if all you have is a 10mm socket and 12mm socket, you can take 1/2 the truck apart. It just might not fix it!

I've been fighting P0171 for over a year.
Replaced:
O2 sensors - no luck
air filter - no luck
fuel filter - no luck
pcv valve - no luck
fuel regulator - no luck
tested all injectors to be good - no luck
tested MAF to be good - no luck
Fuel pressure at 40psi and 70psi if I pinch the return line so the pump is prolly good - no luck

New Denso MAF on order
New Denso fuel pump on order
New Fuel Injector seals on order
I should start replacing 24yo rubber hoses too. Where do you buy those? There gotta be 100 places that have rubber hoses. I'll try Oreillys first. It's just rubber so I'm not going to a dealer for those.

All I know is to keep trying.

 

I'm thinking of 3 things:
Coil on the back passenger side
Spark Plug in #5
Fuel injector in #5