Irrespective of Other people declare of the 20HP or maybe more improve- on modified heads on your own, this is actually impossible with no camshaft or pistons improved. Toyota has casted and machined all their four valve heads to very close and correct tolerances for street (and rally) use. The https://landenelirg.blogdeazar.com/26868822/4age-20v-turbo-engine-for-sale-fundamentals-explained