Ok yall....I have a 2000 mustang gt that I have purchased recently and have run into a snag. I am going to be replacing the spark plugs and am stuck as to which ones to purchase and install. Every store i go to gives me a different plug to buy...from NGK to Bosch to Motorcraft! I am not what u would call "mechanically inclined" but i am learning fast and my new mustang has a couple of aftermarket things done to the engine like a K&N cold air intake and i believe aftermarket plug boots. I am trying to get the most horsepower increase i can out of a plug without messing anything else up. I want to put premium plugs in for the best performance. Any help will be appreciated. Thank you.