be aware Pauls rollers are known to be very accurate,so out right power might not be as much as your expecting, but i will guarrantee he will get the best out of it.
Other places might say you will get 'X' amount extra, dont listen to any of that b****cks, just take it that it will be more powerfull, by how much im not sure as every car differs, but it will come away being better!
Price depends, I think around £350 for a live map, dont just get a 'chip' as it will be not far off that price and will not give as much