A side view of 1997 vs 1998 LS400 cylinder head..The 1998 intake port is considerably more efficient...However, I am contemplating extrude honing process of the exhaust ports to reduce surface area , thus reducing exhaust gas heat imparted into the aluminum cylinder head. Probably will follow up with secondary thermal barrier coatings. Expect 20-30 rear wheel horsepower gain (less heat means less propensity to trigger knock sensors thus iECU will maintain greater ignition advance across the curve)