My car is already four years old now, and so I am now deciding to replace the battery. I just want to know that will I feel any performance increase by changing to a new battery? Can someone tell me what is a good battery for my car (impreza'99 2.5RS)? price/where to buy?

Yesterday night, I won my friend's volvo S40 1.9T from 0-100 by half a car. However, my car seems to die down after it reached 100km, and then my friend's S40 passed me =(
Any suggestions on how to make my car go faster after 100km? My current mods: air intake, and pulley. Thanks!

 

Nope not unless your talking about the performance of something like a high power stereo. Of course you could get a smaller lighter batter like the Dynabatt battery which is about 1/2 the weight of the stock unit. However I still doubt it would be a big enough weight difference that it would yield some kind of gains. When your cars running the power comes from the alternator.