Fuel Economy Tuning: new member

I'm new here. Hi.

I just let go of my 1988 22R stick 2wd Toyo for a 1997 2.4 automatic Tacoma. The '88 got 22mpg city driving in the winter - the '97 gets a whole 18mpg. I have not yet taken it out on a flat land road trip to count highway miles.

Compression is 200-185-190-190. Haynes book says 178 psi is standard and 127 permissible minimum.

What I've done: plugs; cap; rotor; wires; fuel filter (it was the original); r/r cracked exh. manifold; front 02 sensor; checked and cleaned EGR; r/r air filter(disposable) and checked that my bad cat is at least not clogged.

I also ran Seafoam down a center vacuum line.

My only code is P0420-cat efficiency below specs. Since the thing does not smell like it's running rich, I'm gonna ignore the code until I get my MPG's up.

I have not yet put in a racing air filter. And someone before me tore out the charcoal secondary filter.

Can anyone add to my lack of wisdom? Thaaanxxx, dan