bro...this issue had been discussed quite some time back too..
but in fact, bolt on can be very powerful too...it depends how deep ur pocket can go...
infact, there are some good BOT kits selling out there..the essential thing is that u will need a better management, u need more fuel..
and yea..u are on stock compression pistons that are relatively high in compression ratio...i think stock ones are 10:1.so maybe u can lower it by fitting in a thicker metal gasket..
as long u have sufficient fuel...0.5 bar shouldn't be a prob even if u dun change ur pistons