Tuning the carburetor can make a big difference. Make sure you are at an optimum fuel/air mixture because if you are running too rich, you are losing hp. Make sure your air filter is not too small and restricting your air. An appropriately sized K&N unit will help if you are not running one already. A less restrictive exhaust/muffler system will also help you gain some hp. You should figure a minimum of a 20 per cent parasitic loss with accessories and your transmission. So if your ZZ4 is rated at 385 hp at the flywheel, then you should expect no more than 308 hp at the wheels. And that would be best case scenario.