car modification n fuel consumption

[sam1741]

hi all..
why there r many ppl.. without knowing what u modify
will straight away say "Sure makan minyak one la"
no matter what modification.. sure say 'FC INCReaSE' one

modify open pod air filter, FC INCREASE
modify straight muffler, FC INCReASE
modify straight through exhaust, FC INcrEASE
removing cat, FC INcreasE ( <-- i strongly not encourage, cause i m greenpeace member)

modify what also will say increase in fuel consumption

the more silly thing i heard is sound is louder, petrol is louder.. :?


so i wan to ask sifu sifu here who got modify car before
is it true or not?
really fuel consumption increase?
or is it because change of driving habit? hunger for the good feeling when power come...?



logically thinking
if modify exhaust, example straight piping, better flow muffler

than the engine actually need less energy to push the exhaust out through the pipes... how can it be more fuel consumption..?

example changing to better air filter, and do a proper setting
so idle and during driving we having same RPM.. how can be increase FC
plus better air flow, means the engine actually need less energy to 'suck' the air inside... how can increase fuel comsumption..?

i just very curious...

??