A VFM in the long run.

I have purchased a Verna SX ABS in sept 07.It has done 10,000 Kms and have finished 2 free Services.
I have checked the mileage when it was 2000 kms i gave only 10 kmpl in city and highway 12 kmpl,the same even now.
When enquired i was told the engine needs to be fine tuned and will be done only in the 2 nd service.
My kind of driving in city limits is below 2500 Rpm and on highways between 100 -120 kmph.
The automatic climate control ac when switched on it intakes outside air which is a major problem which cannot be rectified since it is a factory setting.So you have to change the circulation mode manually.
There is a suggestion,for the above problem.
Instead of pressing the auto ac switch,you turn the temperature setting knob either left of right with the recirculation mode in inside mode so that i will automatically go to auto mode and will not change the circulation mode setting.

Pls suggest whether i can put K&N air filter for my car.Will it improve mileage.
If i install  pete's tuning box for my verna will it affect mileage since there will be an increase in performance.

Your views pls.