i was talking to a guy with a 500rwhp r33 skyline who was telling before he built the monster he had that he ran his stock turbo on 18psi for 2 years and it was still perfect when he took it out of the car. He was saying that its all about have the supporting mods to ensure the turbo doesnt deteriorate eg a big exhaust to let the heat exscape fast, Good intercooler, ect ect. I wouldnt want to try it myself but he knows his shit and managed to make it work some how....