The amount of horsepower added by a cold air intake and exhaust system varies based on several factors, such as the make and model of the vehicle, the quality of the components used, and whether any other modifications have been made. Generally speaking, installing a quality cold air intake can add between 5-15 horsepower to your engine's output while an aftermarket exhaust system can add another 10-20 horsepower. In combination with other performance upgrades like upgraded headers or a tune from a professional tuner, you could see even more significant power gains. However, it's essential to note that these figures are just estimates and will vary depending on several external factors such as driving conditions and altitude. Ultimately if you're looking for an easy way to improve your car's performance without breaking the bank then upgrading your air intake system along with an aftermarket exhaust is one of the best places to start!