Hi, I would appreciate any advice from the experts here. I have modde my 33 GTR to about 600 hp using HKS 2540s etc. High boost is 1.5 bar. The tuner has installed HKS S45 plugs and it seems fine. But the local HKS guy advised that S50 are needed. Otherwise I could fry my pistons on high boost! FYI, I run the car at 1.2 bar everyday and on track day I intend to run full boost.