Despite others claim of the 20HP or even more boost- on modified heads by yourself, this is actually not possible without camshaft or pistons improved. Toyota has casted and machined all their four valve heads to very shut and accurate tolerances for Road (and rally) use. You will discover as https://4age-20v-for-sale99999.blogstival.com/49143062/indicators-on-4age-blacktop-engine-for-sale-you-should-know