bro sk2, since u plan to turbocharge it....
so best to to opt for GSR pistons as its low comp....
if u r uncomfortable to bore ur block, u can go look for 4g92 block as its already 81mm....
but if u r planning to change block, might as well go get a GSR complete block???
Fdaneil....from calculation, ur FC seems to b on the high side...
but, wat is ur driving style like??? also for city drive or cruising on highway???
if i remember correctly, last time my 4g91 able to giv me at least 11km/lit regardless of driving style.....