For those of you turning up the boost on your motors, I thought you might like to know we now have a full lineup of BOTH rods and pistons for the R18 and the K20Z3. Previously, rods for the R18 were a bit hard to come by, and so we're glad to have them finally available.
In general, you should probably consider rods and pistons if you're going over about 8 PSI of boost. You should also select a piston with a compression ratio of less than 10:1. It will help ensure that your motor holds together in the long run. For K Series motors under an extreme amount of boost, we recommend choosing an "I Beam" style connecting rod.
More info on the pistons: Honda Civic CP Pistons Forged Piston Sets
More info on the rods: Honda Civic K1 Rods Billet Forged Connecting Rods
Let me know if you have any questions. Thanks!