Spark plug service cycle is 4 years so those are due but I doubt it's your problem.

As mentioned, get some CRC MAF cleaner at Pepboys or other auto parts supply and clean MAF.

You must remove MAF insert to clean. You need a Torx Plus (5 point ) TS45 security bit to remove mtg fasteners. In a pinch, you can grab the edge of the 'washer head' screw with pliers or vicegrips to remove.

You don't say but what is your gas mileage. A lot depends on how you drive. I'm guessing the mixed/city driving is in a range of about 15mpg to 19mpg for most drivers and highway is 23mpg to 30mpg. That would be an average over several tankfuls using the miles on the trip odo divided by gallons pumped.

Another thing to investigate is the O2 sensors which usually start failing at about 100K. There is a procedure for checking the electrical characteristics of the sensor but I don't have it currently. Eventually bad O2 sensors will throw codes.

Finally, have you considered that you just have a worn engine. Most engines can't produce as new mileage as wear takes a toll on compression, injectors, etc.

Good luck.