ENGINE REBORE AND NEW PISTONS

[smokeybandit]

I hava 325is 1989,and its not as powerfull as a few ive driven before.someone reccomended i got the engine rebored and new high pressure pistons or vaves.and this would add an extra 20-25 bhp. is this right,and if so,would i need the engine out of the car to have this done and would anybody have an idea of a rough price for doing this.any info about this would be greatly appreciated.thanks