I have a 97 F350 7.3l diesel with a 4" MBRP exhaust on it. I was getting a loud drone between 90 & 100kmh which only got worse when towing my 5th wheel. I installed the Twister and I am thrilled with the result! It more than met my expectations. Add in the great price and free shipping and I would highly recommend this product. I also received very timely advice via email. I will definitely keep BC Diesel high on my part supplier list!!!