Fuel economy Q

[jing]

I used to average roughly 450-500km per tank of gas, filling up usually around 50L each time which equals out to around 21-23.5mpg.

Now I average around 400km per tank.. or in other words, roughly 19mpg.

What can I do to increase my mpg back to what it was before?

Here's what's been done so far:
- reset timing to stock @ 15 degrees (it was advanced before, my mpg decreased AFTER it was set back to stock actually)
- replaced stock pump with walbro
- new nismo fpr @ stock fuel pressure
- new fuel filter
- new plugs gapped @ .032 (stock boost)

I should also mention that my driving style has not changed much, if at all since the decrease in fuel economy.

Specs:
Redtop SR
Splitfire coils
PBM cobra pipe
3" catback exhaust
3" test pipe
FMIC
HKS SSQV vented to air