With a 34 I'm running 19psi every day (spikes to 21psi briefly) with no dramas whatsoever. As long as your AFR's are perfect you shouldn't have any probs running around 20psi on your car with a 34... Might want to consider upgrades to TMIC, fuel pump, exhaust, intake though if you want to get the best out of that turbo...

cheers

Brett