Hi, I belive that the standard head gasket of a N/A is 0.8 mm thick. I have seen a TRD headgasket for the 4efe which is 0.6mm thick. You can see where is going. I will have the following supporting engine mods before the gasket goes on. 1. HT Leads 2. Air Induction Kit 3. 2 Inch Cat Back System with No Middle Box. 4. Corolla Inlet Mani 5. And possible OBX Manifold Ive probably missed some things. I know that the thinner gasket will raise my compression ratio. But what will the benefits of it be. BHP/Torque wise. Estimate with and without OBX as its not a defo at the mo. Lastly do i need to make any additional mods for the TRD Gasket to be fitted? Thanks