I took my cores out and welded in some washers that fit inside the core. The washer wher also cut in half and staggered all the way down the core tube. Try to find non galvanized washers just plain steel with oil coat is best. Zinc is ok. The pipes where so much quieter. Power was still the same. I think 8 or 9 half washers per side. And also had the spark arrester too.