http://www.phatka-t.com/projectcars.htm
Looks like with perfect tuning, the ring lands usually give out around 400whp just from pressure.
http://ka-t.org/ipw-web/bulletin/bb/viewtopic.php?t=879
http://nissaninfiniticlub.com/zerothread?id=92521
These are good threads to see what usually goes wrong and what causes it. With forged internals, there really is no limit. At least nobody has really hit a brick wall. it all comes down to tuning. Stock internals are pretty safe to around 300whp(12-14psi) if they are in good shape and you have a good tune. Sure it is possible to go past that on stockers, but how good of a tuner are you?