fuel problem

[willystheory]

So I looked at some of the other posts and they did hint to some good ideas to check out,but I figured I'd still give my own thread a shot.

Some time ago I did a basic fuel system cleaning, seafoam and premium gas, really try and get some stuff burned up. Prior to this I could get anywhere between 300-320 miles per tank. After the cleaning it went down to 240.
Well I figured it was residual premium and seafoam in my tank and I'd just wait it out.
Since then it jumped back up to 300, then for no reason it plummeted back to 250.
SincE then I've installed anew cold air intake, plug wires, break pads and rotors. I've been holding steady at 260/tank for 3 tanks now.

What happened to my mileage?

97 civic ex 1.6L

 

[2slo4u]

Put the stock intake back on and see if anything changes. Could just be driving habits

 

[willystheory]

unfortunately the air intake was put on after decline incline and again decline, and my driving habits have not changed in the whole year and a half that I've owned the car.

 

[taluzer45]

Could it be a injector issue?

 

[willystheory]

I was thinking that, but I'm not very knowledgeable in the fuel system and don't even know what I'm looking at.