Low MPG, at a loss
 

So I have a 1999 Accord V6 with 167K miles on it.

note: I just spent about an hour searching google and other forums and couldn;t get a straight answer

It seems no matter how I drive( i mostly drive highways) I get about 20mpg, actually thats what I get no matter what. Everyone else says they get about 28

I have or it feels like i have the same torque and acceleration I've always had, sometimes it dosent give much torque until the v-tec engages(rarely happens)

My plugs look in good shape(NKG), they are gapped at .40

my air filter is slightly dirty

I'm not entirely sure but i think its a clogged injector, but i want some opions before i go and rip off the intake manifold cause that is a big pain

Also idk when the plugs where last changed, could they casue that steep of drop in mpg?

Thanks for anyinput

I would suggest starting with seeing if there are any codes stored in the computer, some of the automotive parts place will run a check for free. Gas mileage seems to have always been a mystery. I would think one injector to be bad enough to cost 8 miles per gallon would give you an engine miss. I would have to see the spark plugs to give any kind of answer on that question, but if you have no codes I would do a tune up, check the tire inflation and start there. When did the mileage drop off? The trans is shifting into overdrive if you have an automatic