Video of noise.
 

I'm hoping it's not rod knock, I can also hear what sounds like valve tap. Give this video a listen and let me know what you think. Thabks

https://youtu.be/O8iJ53kQ580

Hhhhmmm.... not really sure. Does it just rattle a bit when you are letting off the gas?

The truck sits allot! I only put 1800 miles on it last year. The noise I'm more concerned about isn't that tap tap tap you hear after I touch the throttle. It's that other knocking noise. I can hear it better with headphones. Try listening with headphones

Sounds like a bad cat to me. That's how both of mine have rattled. Crawl underneath and listen right under the cat.

I don't have headphones. :) Not to mention, my hearin' ain't the best in any event. :D

Slide under while its running, if its rod noise you'll hear it at the oil pan. You could try some oil conditioner to increase the viscosity, sometimes bearings get worn and providing thicker film removes the noise.

Truck is catless.

I'll have to get under there while it's running and see if I can pinpoint the noise and where it's coming from.

For the last 2 oil changes I've been using Pennzoil high mileage full synthetic 10-30 and a k&n oil filter. What viscosity would you recommend, it gets pretty cold here in the south eastern corner of PA.

First make sure its rod noise, I don't like additives unless they are necessary You could also get your oil tested to see what is floating in the oil. I've sent a couple samples out, one that was mine from new - now with 80k on it, and one I bought for the kids at 100k. They remarked how the first was super clean and didn't show particulates for the miles on the oil... the used car showed some issues that I was to keep an eye on. Kinda interesting stuff.. There are a few labs out there, this is the one I used ...
https://www.blackstone-labs.com/

Shoot, I've been using 10w40 since about 2010 from MN to TX to WA. Even ran 15w40 diesel oil for awhile. You'd be fine going up to at least 10w40.