I had hear that for normal road cars that it was kind of a myth and a waste of money. Better spark plugs would be a better choice like E3 if you want more power gains even if it is small.
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For I know the plans I have for you," declares the LORD, "plans to prosper you and not to harm you, plans to give you hope and a future. Then you will call upon me and come and pray to me, and I will listen to you. You will seek me and find me when you seek me with all your heart.