Irrespective of Other folks claim of a 20HP or maybe more boost- on modified heads on your own, this is solely unachievable without having camshaft or pistons altered. Toyota has casted and machined all their 4 valve heads to pretty near and exact tolerances for Road (and rally) use. You https://andrevxwvp.ka-blogs.com/79951943/rumored-buzz-on-4age-20v-turbo-engine-for-sale