Pick-up of my Hyundai Santro Xing is very poor, what could be the problem?

The acceleration of Santro Xing will stay the same even after the replacement of any of the mechanical part. This is because the petrol cars with engine sizes below 1500 cc mostly face the problem of lower acceleration while the AC is on. The extra load of the air conditioner makes the car slow and under powered at many points. The same problem can be faced in Maruti Suzuki's Alto 800 and Alto K10, which are very responsive without AC and gets down whenever the AC is turned on. Avoiding the ill effects of AC when ever overtaking on the highway can be done by manually switching off the button before overtaking and pressing it again afterwards. Using good fuel and genuine parts can increase the life of your vehicle and would definitely be a good option for a long term use.