I use Iridium plugs in my 72 Bonneville and also my 70 BSA Royal Star. With non-resister caps. The Bonnie has a Boyer, the BSA, points. For both bikes the recommended plugs are Champion N3 and N4's respectively. I too was skeptical about any performance enhancements, but was told to give it a try by a Brit bike guru. Sure enough, both bikes have seen an improvement in starting, idle and cleaner running with less fouling. They have been problem free. For me, it's worth the few extra bucks.