I think that 4 banger is doing very well, I don't think the gears are going to help, they're just going to get your RPMs up and you'll end up with the same speed. Just think about it, it's only got about 150 hp. jmo
Welcome to the forum
I'm not sure but I believe all the 2000+ V6 Toyota trucks have chains.
Yours is a chain as well.
Have you tried running fuel injector cleaner through it? I would try Seafoam in the gas tank, I use a lot of Seafoam in on my combustion engines.
Personally I think it's a waste of money, all A/M exhaust for our trucks sound like fart cans imo. I do have a K&N drop in filter for all my vehicles because I can't see buying new filters every few months.