I've heard in the past from a toyota tech friend that the 3.5 has gone over many updates since it was produced around 2004. Only other small thing I've heard is the pistons had a couple more compression holes around 2018 for the 3.5 engines. I guess it allows less chances for the oil rings to stick, and carbon up. It's why our dealer here likes mobil1 ep for those engines...they have a great detergent additive package, unlike some cheaper synthetics.
As far as the 3.5, there's a zillion of them out there, where you're bound to get some clunkers. You'll always hear the ones that complain the loudest on these forums that got burnt. I see more 3rd gen tacoma's of all years on the roads here than other gens combined. I've got nearly 37k miles on my 2020 3.5....not a single issue.....been flawless. Idk whether it had to do with being built in texas but the truck runs better than most 3rd gens out there.
