Toyota Repair: 2000 4Runner problem, fuel consumption, canal water

Question
My 2000 4runner had a check engine light with a obd code of p420.  I took out the MAF and cleaned it very well, out it back together, reset the code and it ran fine for about 2 weeks.  I then got another check engine light.   Don't remember what the code was but the internet was saying that the catalytic converter needed to be replaced.  Other posts on the internet was saying to replace to O2 sensor.  I kept resetting the code.  It would stay off for several days and then come back on.  Finally I got the code that says the O2 sensor was bad.  I replaced the pre cat O2 sensor.  The check engine light has stayed off this time, but the truck idle is bouncing and it sounds like it is going er er er to get up to speed.  Also I gas up every day from my commute which used to be 5.2 gal to refil, now it is close to 6 gal.  Can you help with this.

Thanks,
Nevr2late

Answer
A fraction of a gallon is not that much more fuel use. You will use more fuel as your engine increases mileage and usage. The most common factors for fuel consumption is how you drive the vehicle. Another factor is outside temperature. Additionally, the quality of the fuel we use these days is not all that great. In my opinion, it's just a few molecules away from being canal water. An 8 year old vehicle would most likely not need a cat replacement. I would recommend that you visually inspect the plug wires and possibly have a tech test the throttle sensor. For the time being, use a higher grade of fuel.