Mileage dropping quickly.

My 98 GTP always got about 18 MPG. Added a Thrusher air box, 3.4 pulley and new rocker arms. Mileage dropped to 16.5 over night. Now it's at 15.7. Driving the same as always. If this keeps up with the price of prem. I'll be parking it and drive my GT. Any ideas?

i'm guessing that your battery was unplugged and your dic was reset so it's basing the new numbers off your currenty driving habits. drive it like you normally did for a while and it should get close to where it was.

Haven't changed driving habits. Battery was not unplugged.
Filled car Friday. Drove a little over 40 miles. Now below full mark. Car reading 15.6 MPG now.
Think with more air, goes more gas.

Sounds like something is off. I see around 17-19 w/ more mods then that.

I just bought a Neon w/ 138k miles for $350 that I'll be using for driving back and forth to work.

click sig for mods