[keithmac]

I turn mine on at 9psi, I have a safe tune up to 8psi (wastegate pressure) and a more agressive tune starting at 11psi which needs water/meth injection active.

Depending on how quickly your car builds boost it may be good practice to keep it at 12psi to cover the "lag" time for the WI as Dust said. I have a 1-2 second lag between pump active and the mixture actually hitting the combustion chambers and affecting the AFR and the two small turbos 9b spool up very quickly.