im having some issues that are bothering me havnt figured out yet

vehicle 2002/6spd

issue #1- fuel mpg (displays 21.0) actual is about 18
question - what is causing such a drop (before all mods i got around 27)
-please do not say.. my driving habits or anything that would only have a minor effect on mph
possible- could maf be playing a part(attempted cleaning),throttle body? has any experienced major mpg drop from knock sensor?

issue #2 - lack of power esp. low end

mods- obx headers, cattman catback, 3.5" intake & maf housing, bop, safcII tuned, nwp spacers, velocity stack/blox filter, fidanza flywheel
maint.- new plugs ngk, 3 new coils, new pcv, and fluids

took the car to the track, on street tires spinning first and 2nd only ran a 14.4 and that was pretty consistent
(and i have raced before plenty of times, this is not my first run at the track)
other info- fuel- 91 or 93 octane, iv cleaned my maf sensor, when i was at stock maf housing still had same issues

my concern- car feels like it has nothing until 3.5-4k rpm, does burn some oil but not a ridiculous amount, it just feels like its not full potential esp. considering the mods i have. it may not make much of a difference but i ordered a fuel filter from nissan so that will go in when it gets here.
- im also fully aware that the motor isnt one for low end power but this is an obvious decrease in power

*have not done compression test yet, but when i go back to work next week(currently on vacation =D!) ill do a compression test

if anyone can chime in and possibly give me some insight it will be appreciated , i just feel kinda stumped. esp. with the mpg, and 1/4 mile time

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Anyonee

 

The mpg calculator is usually about 3-4 mpg's off.

What kind of exhaust do you have?

 

Thats why I noted actual about 18 and obx v2 and cattman

 

I had the same **** happening to me after I cleaned my TB... Those drive by wire TB are sensitive... I replaced it and MPG came back to normal.