HELP - Palio giving low FE and poor performance (1.6)

[lamborghini]

Hey guys,
we have a 2002 Fiat Palio 1.6 GTX which has clocked 43000km.
Over the last 2000 - 3000 kms, we have faced a couple of problems.
They are -
1.
The car isn't picking up as it generally does. It improved after a tune up and filter change but still not GTX like. Its like Indica Petrol in terms of performance.

2.
The average has gone terribly down. Earlier, the car used to give us 8.5 - 9.5 kmpl, then it started giving us 6 - 6.5kmlp and then after the tune up, it gave 7.5kmpl but then the odometer got messed up again and it's not working properly but i have a gut feeling its gone down again. According to the odo read, it's giving less then 5kmpl but if i try to figure it out taking into account the odo is messed up, then it's giving us 12 kmpl which is too much considering that it needs to be refuelled very often.
According to the odo, the distance from the petrolpump to our house is 0.7km wheras according to the odo of teh fiesta and lancer, its actually 1.7 km.

I have a feeling that the fuel line maybe leaking but no evidence to support my feeling.
It's going to the garage this coming Monday, the 19th so i need your help ASAP.
Thanks and Cheers.
Lamborghini