ok seem like less then 3 years ago i could get about 350 miles a tank outta a full tank of gas(roughly 55,000 miles on the car)

Driving habits havent change any

maitenance has been on time or very close to

had changed out the spark boots to iraduim type rk sport sells at 35,000 miles(since ecotecs don't have plug wires only the intermediate conection)

tires have been kept up with so air presure has been good

and i travel around with about the same weight of items aside from about 60 lbs of turn out gear

since about 18 month ago im now down to 280 miles a tank

i've changed the plugs at 88,000 miles and tonight put the old factory spark boots back into the engine taking out the iradium ones that had been in tonight

Oil change is coming within weeks

new fuel filter is coming with it

have an intake on the car but it's been in the whole time even before i lost mpg(could get 25mpg with it in)

any other ideas as far as mechanical reasons why my mpg is down

i do all city miles(91,000 miles as of today)

Carbon deposits, normal wear and tear on all moving engine components, cam lobes, timing chain (valve timing MAY have changed). Piston rings and cylinder walls wear, compression may drop slighlty.

How many gallons per tank? Do not trust your fuel gauge to know when you are "empty". Has your fuel in your local area changed to E10 in the past year or two?

Check your plugs. If they're black check your IAT sensor.

yeah far as i know when they droped the mtbe they went 90% gas 10% ethonal , plugs had a litte bit of carbon on them when i changed to the news, the ait is ok is there anything specific that im wanting to look at , im planing to run some seafoam once i get paid to deal with the carbon