I have this mod on my 2001 4.4 and I removed the resonator as well. I like the sound; however, during hard acceleration there is annoying sound as well. It is hard to describe but it sounds like a clicking sound. It has more to do with the resonator delete but I placed the X-Pipe in place of the resonator for a nice low exhaust tone. It really is not that loud and I'm not in the gas flooring it all the time so I live with it the way it is now because 95% of the time the X5 sounds sweet.