i look to intake and exhaust mods.
My economy was piss poor when i was driving 10 miles up a severly windy mountain with a cone intake. I got about 170-tank. Now, with what is basically a stock airbox doing the same use, i get about 240, around town i get about 350 (356 to be exact
). I'll admit im a bit of a throttle jockey though.
--real information starts here--
Floppy exhaust and intake make the car idle less fuel efficiently than ideal, they also affect your low end, the car loses its smooth flow of air. Try blipping the throttle to see this effect. Beyond the point where the vacuum is filled by sucking from the engine rather than the spreading of the atmosphere (i hope that makes sense) is the only time when large exhaust and intake is benefitial to power and economy.
i would look at would be things that mess up the even supply and correct ratio of air and fuel. This would include not enough fuel because of an old pump, poor dispersal by craptastic injectors, any air/fuel/exhaust monitoring sensors, cat, etc.
Your last possibility is to check if you have some horrid parastitic loss. Too thick fluids in a tranny, engine, or diff, binding brakes (doubt it).
This is probably way further than the problem is, my guess is the mods or a direct result of the mods, like a dead maf or something. Good luck.
