Fuel Economy is getting worse

I have a 2007 DC TRD Sport Tacoma with 34k. I bought it used as a Toyota Certified Pre Owned vehicle, but out of bumper to bumper warranty due to year.
I usually take it from mid Florida to south Florida down I-95 once every couple of months. I usually do between 74-78mph and usually get 350 miles to a tank +/-.
A few weeks ago I took it down and doing the same thing I always do I got about 250 miles to a tank. In the city lately I've noticed the fuel economy has gone from about 300 miles to a tank in the city to about 250 in the city and I have purposely have been taking it easy (keeping RPMs below 2k, etc). I recently put more air pressure in the tires and I don't know may have caused it though I don't think so.
Yesterday I noticed that itwas kinda shaking while idling....like it was running rough. Dunno what the problem could be. Just had it's 30k service and I maintain it well. I am not mechanically inclined so I'd have to take it to a Toyo dealer if need. I do work at a dealership (not Toyota), so if I could troubleshoot the issue maybe one of my mechanics could work on it here.

Help? Thoughts?

Thanks.

 

were the plugs replaced when they did the 30k service?

 

No they were not because I was told by the Toyota dealer that it was not part of the 30k service. Though I thought about that .... is it fairly easy to replace those?

 

Changing Spark Plugs

 

If you paid for the full 30k mile service it should have been included. If you paid for it, you might want to bring it back. It's easy enough to do on your own though.

 

Air filter? Go to autozone and spend $10 on a digital tire gauge. 29 and 32 are what my truck uses. Don't over fill. Also rotate the tires at least every 7k. Also could be a broken plug. 34k is not that much so I doubt the plugs are gone.

 

I got the service done at my dealership for less than half the cost of what the Toyota dealer wanted. Of course I get employye price and parts at wholesale so that helps. I will look into changing the spark plugs.

I have a AEM dry flow air filter. I rotate tires every single oil change. I will make sure they are between 29 and 32 ....

 

Darn right spark plugs are included at the 30,000 mile service (it's in your owners literature)... ~$500 is what the dealer is charging me, less a discount coupon for my 30,000 mile service today.

 

It could be the plugs or something that shook loose after you got the 30K mile service. With that few miles you shouldn't be experiencing any rough idling so something IS wrong with your truck.