3. Although MSD recommends the O2 sensor bung be welded in, we decided that this clamp from Summit Racing would be a much easier solution. The clamp uses header-quality gasket material, all stainless hardware, and will fit pipes from 2.75- to 3.00-inch OD. If this clamp poses an issue later we will just weld in the bung, but we have used these before without issue. Plus, we didn’t mess up the ceramic coating on our headers.