Good Idea on the 93 and octane booster, PCV valve is EASY to replace.EGR valve needs replace or clean...possible fuel pressure issue and or dirty injectors....1/4 tank of 93 and a entire bottle of 104 octane booster..but possible that the PCV valve is on that side may be the problem too..check vacuum hoses to the booster and the vac rail at idle with soapy water and spray bottle..you will find it when the idle raises a bit