Max boost with stock turbo

My interested in the question as well. I'm currently max'd out at 14 psi on my 85 GN. This is with premium unleaded (93 octane).

I'm pretty much stock except for a large Intimidator air filter/intake that was installed by the previous owner.

Is the 20 psi with a higher octane than 93?
 
Boost

"Good gas" means race fuel, there is no good gas for the street except, homebrew or premium w/ alcohol injection. Either way the stock turbo's effiency is done after 20 psi.
 
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