How much horse power does a flow master exhaust kit add to your truck?

A Flowmaster exhaust system will not add any significant horsepower to your truck, and in some cases, may even slightly reduce it. While it might improve exhaust flow, the gains are usually minimal, often less than 10 horsepower and frequently unnoticeable without sophisticated testing. The main benefit of a Flowmaster exhaust is a change in the sound of your truck's engine, not a significant increase in power.