ECU reset gas mileage

[2.5T_/<ouki]

Start you off with a bit of info on the car.

S14 w/ RB25DET
- Rebuilt
- Greddy Intake Manifold
- Intake
- FMIC w/ HKS BoV (non recirc)
- Stock injectors / turbo @ 10psi

I granny drive my car and I'm only getting about 200 miles to a full tank of gas, so i decided to search around a few forums (including this one) about such situations and noticed everybody saying they reset their ECU and it makes a huge different in upping the overall gas mileage. This is not the case for me! My gas mileage has gone down by 30mgp; I'm not sure if this is a coincidence or there is something wrong with the engine and it's getting worse? Would an ECU reset do this type of thing?

Curious to know if you guys would point me in the right direction of where to begin when it comes to fuel management and overall fuel economy.


Things to check
- o2 sensor (purchased BNIB 300zx tt o2 about 5 months ago)
- MAF
- Coil pack

is there anything else i should be checking/looking for? What would cause me to have such horrible gas mileage? I know running the stock ECU isnt really helping, but i figure it should be more than 170-200 miles to a full tank of gas considering i GRANNY drive my car.