I'm thinking about purchasing a nx proton plus system. Is it safe in a 2.5liter duratec mercury cougar?

 

As long as you keep it at a safe HP level such as 50hp then yes it will be perfectly safe. You will want to run the car on 93 octane when you plan on spraying and i would recommended running one step colder on the spark plugs.

If you would like feel free to shoot me a PM or call in here and i can quote you a price.

Trey