actually many upgrades will improve reliability because the aftermarket products are made and designed better. First you will notice a huge gain from a cold air intake. If you live in a rainy place you might want to go warm air or take off the bottom pipe to save the worries. things such as the sct or sct computer upgrade will also give better performance while making the engine run much better. I am sure you will get many responses on this, but there are a lot of mods that will improve the car.