Just installed an Akrapovic slip-on. I also ordered a set of their spark arrestor inserts. Each insert has a 6mm threaded hole and comes with a bolt. But there are no bolts holding the original inserts in place. They appear to be held in by a spot weld on each one. The spark arrestor kit didn't include any instructions. My best guess is I'll have to drill out the spot welds, pull out the tip inserts, and then install the spark arrestors with the bolts. If anyone had experience with this, I'd sure appreciate some advice. And by the way, if my guess is correct on the install method, it sure is cheesy for a system this expensive!