[LaxMan]

jonnyk is right about being relative........

I have 60cc chamber Darts with fly cut pistons and I was able to run 9 psi with a chip. (Powerdyne 11lb pulley and their chip).

I was also able to run 11 psi with a T-trim with a stock pulley
BUT!
When I went to a 2.85 blower pulley (13psi) I melted 2 piston.

All of this was with 93 octane.