how does 20psi correlate to needing new axles? 20psi on what turbo? 20psi is just a measure of pressure, not power, for example 20psi on a vf10 may give you 200whp, while 20psi on a GT40R would give you 500whp. now that we are done with that lesson, as white2.5rs said, you should be fine on stockers
more specifically i bet you will be fine up to 300whp+, it all depends on how you drive.