Regardless of Other folks assert of the 20HP or more increase- on modified heads by yourself, this is actually unachievable devoid of camshaft or pistons modified. Toyota has casted and machined all their 4 valve heads to pretty shut and correct tolerances for street (and rally) use. 4Age 20V Turbo https://blacktop-4age-for-sale01531.bloggactif.com/27298011/5-simple-techniques-for-toyota-4age