there are quite a few guys running 15-17 psi on their stock blocks with various turbos/manifolds. the tune and what fuel its tuned on will determine how much boost you can run. Nobody has popped a motor yet from running too much boost. unfortunately it will take someone blowing there stuff to find the limit.
side note- i like how the ebay manifold guy is a friggin expert on boosting this motor all of sudden lolololol.
I also stated without mechanical failure, because some things are out of your control.
K series has a much better oil pump design than B series (chain driven pump won't shatter a gear due to harmonic vibration like the B's suffer) so you don't really have to worry about an oil pump failure.
But something like a failed wastegate (which would cause boost spike) could pop a motor. again there are precautions such as setting up boost comp tables and using a boost cut.
Injector failure is always possible and pretty common with aftermarket injectors.
Using a high quality injector such as the Injector Dynamics will help rule this out as well. I've seen stories of even brand new RC injectors not being flow matched, which will cause some cylinders to run leaner than others. most tuners dont tune on the edge and allow for something like this, but again, when you are pushing the motor to the limit you may run into problems. Hondata does not allow for individual cylinder tuning, as a standalone does. But unless you are monitoring EGT's at the exit of each cylinder port, you don't know which is running leaner/richer.
Fuel pump failure, such as the 255 intanks, sometimes do some weird things. constantly running your car low on gas kills the walbros pretty quickly, and other times the pumps slowly die and don't provide enough fuel, which, as you could imagine, under boost is a bad thing.
theres more but i dont feel like typing it all out lol
on a stock f20c i made 489whp at 16lbs using a 60-1, stage 5 wheel
this was on the dyno on a 90+ degree day, IATs were up there. it easily puts down 500+ on a cooler day.
93 octane mind you. race gas, i believe Rob! has the record at 772whp on a stock internal motor with a 3mm HG.
I know it's a different motor, but the z3 flows very well in stock form, plus it has ivtec which has a much greater midrange torque. This just goes to show you it's all in the tune.