I don't think it's necessary to buy genuine Denso coils, just steer clear of the ultra cheap EBay or Amazon coil pack specials. If you are buying a complete set of 8 for the cost of one Denso at the local parts store, you more often than not have trouble. As the old saying goes, if it sounds too good to be true, it probably is.
I have a couple of Duralast coils in my truck for about a year now without issue. They cost a few bucks less than Denso but also have a lifetime warranty, so even if they fail I have the warranty to rely on.
