Bone stock 200k mile old EJ253.
Right now I'm running 10 psi with 93+torco and a very conservative street tune. It is not even close to detonating - I am sure it has quite a bit more in it , and noticeably more power than 7 psi on 93. I will plan on switching to 93+meth when I get some better gauges installed, maybe exhaust, I am not sure.
Note this is a centrifugal supercharger not turbo, so the boost is high up, I think it is quite a bit easier on the motor than turbo with say 5 psi at like 3000 rpm. I don't hit 5 psi until 4500 rpm.
All the sandrail guys say you can do 10 psi on a stock 253 with race gas, but that is a turbo, not centrifugal supercharger. So I figure 10psi with 93+meth and a centri will be fine all day. It might even be good for 11psi @ ~6400rpm.