I recently removed my cats and installed a cutout and Flowmaster cat-back. The car sounds good at idle and when I romp on it, but when the engine is going through the revs during part throttle it makes a funny sound (around 1800-2000 rpm). The cutout I installed is similar to the Flowtech one, and is just capped off. Do I need to make an insert similar to the one on the Warlock muffler to prevent this sound? I'm wondering if the cutout is causing reversion (and causing the funny sound) until the exhaust starts flowing fast enough. Anyone else have this problem? Any info or tips are appreciated. Thanks