I have a GS300 and it’s stock, I need to know what parts I should replace or add to get the most horsepower out of the engine.

Thank you guys 🙏

 

To get the most?

Everything.

Maybe try this question again but with a more concrete goal, and you will have helpful answers. In the meantime, you can read through the dozens of builds and pages and pages and pages and pages of people documenting their NA-T setups.