I was only getting 27-28 MPG highway and with the price of gas headed towards $4 bucks, I decided to do a major tune-up.
I replaced with Toyota OEM parts ordered from Toyota of Dallas
After using SeaFoam to clean it out (TB/ IAC), I replaced:
ETC Sensor
Both O2 Sensors
Dist Cap & Rotor
New Spark Plup Wires
And a new set of NGK BKR6EP11 plugs.
I just finished a roundtrip of 350 miles nearly all freeway and running 65-70 MPH. I refueled at the same pump, same time of day, and stopped on the second click of the pump handle ( same as the first fill-up).
DRUM ROLL............. Now....34.5 MPG

Highway!
I must say that I was by myself, and it was 60deg. so did this W/O the A/C.
I know this was alot of money to invest, but at todays gas price, It won't take long to recoupe it.
Bear