Has anyone used these plugs and have documented gains, beside "seat of the pants"? I’ve read all the crazy claims and how they will increase fuel economy and HP. I can’t seem to find any believable reviews from independent sources claiming they do anything besides make your wallet lighter. I’ve always been a believer spark plugs don’t do any of that and most of it is all marketing. So, is this just another spark plug gimmick like all the others in the past or do they actually have substantiated claims?