@ 8psi as I ran 26.6 psi last season all year made 585 / 414 and had a tuner that struggled with getting rid of my boost cut issues. I hit boost cut many , many times at 30+ psi .That engine held up very well and was in decent condition when pulled apart with the exception of the valve guides were worn .I don't think I would run 26 psi on a dd but wouldn't hesitate to run 20 psi all day long these things will take a serious beating and 20 psi will make really good streetable power imho however I would recommend putting springs, retainers , and head studs in it .