Custom cams, exhaust and header, high comp. pistons, light flyeheel, light rods, port and polish, bigger valves stand alone or piggy type ECU and a PROFESSIONAL who knows all the small details, and you may reach 200 hp. I started that way ( I reached around 175hp) but it's more expensive and difficult than turnocharging the car. Also it's more work. And you can easily make more hp with the turbo later.