i have a 98 banshee with mild port and polish pc pipes and reed spacers. i want to get a cool head preferibly noss and dont know what size dome to run some say 20 is good on pump gas but could be pushing it. what is the lowest dome size i should get. also i will be adding a pro design impellar and prob a +4 timing advance. Will I stilll be running on pump gas, because wit the port and pipes now i already run premium just because my dad thinks we might as well.