The biggest factor is how you drive. Did you drive the same speed limit as last year? A dirty air filter is a big deal if it's dirty. Not a big deal if it's pretty clean. It could be possible you filled up with non ethanol gas and this year was 10% ethanol gas.

 

don't feel bad..my s10 has normally been getting close to 30mpg but in last month i've gotten new started, altenator, plugs, oil change and air filter and my gas mileage has went down at least 5mpg. i can't tell the difference in my gt, its hard to stay out of the pedal there. Right now, the percentage in ethanol is growing in fuel. when i get gas at an ethanol free station my mileage goes way up. Don't feel bad thinking its your car. Its the gas companies poking us in the gas!

 

I could be wrong, but I thought the TSB was after a "long" trip (about 30-40 miles for me) the car will hesitate when you try to go on the off ramp. The TSB says it is from bubbles forming around the fuel pump. My car does this when I get off the interstate and try to go hard from the stop light at the end of the ramp. If I baby it for awhile, then no problem. I never get a check engine light or failsafe mode, it just dies for a split second and then goes again.

 

Injectors dirty? Maybe try some fuel injector cleaner? I don't know if anybody else uses it but I put it thru my cars about 1 time a year. 2 bottles in 1 tank and the milage goes up some. 1-1.5 mpg.