not completly true uncle ben is running ctr pistons on pump gas and running good on ls/vtec..also get usdm itr pistons for around a high 10: compression.i forget the acual comp but the longer stroke will give you a little better compression.but you have a bigger combustion chamber in your si so you will loose about :2 compression from a grs head.also if you are worried about pinging the best investment you could make is a J&s safeguard.last of all your pistons will make about 11.4.1 compression so dont worry.