I've heard that if you get a PI head swap that you will need to start running 89 octane gas instead of 87 is this true? I heard it was because of the higher compression. How I understand it the PI head swap is mainly 3 things, the intake, cams, and heads. If you do need to run 89 octane with the PI head swap what part of the swap increases your compression so that you do need to run the higher octane?