Wheeey another convert :-) good lad! With 14 psi mate I would consider some kind of forged pistons, and deffinately don't forget to have the boost cut taken out of the ECU, cause a manor a problems. Give me a shout with any questions dude
standard piston will take 15psi as long as you get the fuel right with out problems as long as its the 220/420 engine the 620/820 used dif pistons and are only go for 12psi max my old 220 gsi ran 14psi and never let me down