I put them in at 9K miles. I was like you, read everything I could find on them, thought what the hell, and tried them. I noticed nothing, but I was mod'n and tuning so much I am not sure anyone could have noticed any difference. I kept them in for about 3 or 4K miles, until I started finding articles on how the tips were breaking apart and pieces falling into the cylinders. I think it was a few mustang and f150 sites I found the most negative reports on them, a few guys had lost their motors because of them. So I went back to the good ole' tried and trusted NGK. Trying to get cheap horsepower is just that, cheap. NGK has manufactured plugs for years, done all the testing and tested against numerous other manufacturers. If the E3 was such a threat to NGK they would have already put out a plug to compete with them. These are just another cheap chinese fad. Get the irridium plugs from NGK and build your engine right. Nothing worse than putting $30 dollar plugs into a 3K dollar enigne and having to replace it a year down the road. Just my two cents man, I have tried them, no drastic improvement and the quality scares me.
DJ