you removed both valve covers including moving the alternator and then re-installing it on the passenger side, started engine, loosened nut until you heard clack clack clack, then tightened nut until it went away and then another 1/4 turn, and did that on all 16, correct?

Did you then increase rpm's to verify no more clack clack clack (that's a technical term btw)?

Did you also verify good oil flow coming up through the push rods?

if you were that close, and heard no valve train noise, and did the adjustment as i asked, and verified good oil flow, if if if, then without being there and having to place a bet, I'd go with exh leak or noisy accessory.

Only you know for sure how you did the adjustment and what you observed as well as what you hear under the hood. Youtube videos are good but not as good as being there in person

If you hear the sound from inside the car then you'll hear the sound from under the hood. Snug up the header bolts and listen. After that, remove the belt(s) and run engine for not long and increase rpm's and see if the noise goes away without accessories.

Sure it's a pain in the butt but you need to follow a process of elimination

 

from what will play with this computer today it sounds like a exhaust leak or lose spark plug.

 

wonder ,sounds like i agree plugs wires replace them i think you said you were that should get you feeling better hopeing