put it on a dyno and do it the right way. there is no correct arbitrary answer other than you will probably need to fatten it up a touch. How much? who knows that's what a dyno is for. it is the best tuning tool out there. do it nice, or do it twice:twocents
Dyno tuning is great but if you are not doing anything other then raising compression you won't need to change much. I would start a little richer just to be safe but theory wise, raising compression alone shouldn't lean the mixture.
Having said that, you will get more heat in the combustion chamber so you need to pay attention to potential hot spots that could cause pre-ignition. That can be masked with more fuel but less spark advance is another tool. The shape of the top of the piston can have an effect on rich and lean spots in the camber so talk to someone that has experience with the pistons you choose.
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