Perfomance wise, they will not really give you anything. If you go for the filter, make sure you clean it properly and do not apply too much oil after each clean and mess up with the sensors. You can make a custom exhaust based on the original design or just fit one from the twin exhaust version car.
In any case, before you start using the car hard, check the oil pick up strainer and the injector seals, and read the chain stretch. If any of them gives you sign that your engine is at its last legs, you may need to reconsider with the remap.