How can I get my car to run as best as possible

My truck is leaking oil from the rear and front crankshaft seal due to vibration from a vacuum leak I belief. I fixed the vacuum leak, but since I will be repairing it myself and will have everything apart I want make sure I check everything possible that I can, maybe even improve it, with performance parts if possible or just some pointers of the vehicle I should check. How can I get my car to run as best as possible. What are some major compartments to go over and check. How can I increase the power