I was running Longtubes with high flo cats to a corsa extreme. I experimented and deleted the highflo cats and adjusted the tune for it. Now i get this extremely ugly sounding flutter from my exhaust when downshifting or letting off the gas period. Any exhaust pros in here can chime in on this and help me out. Don't really wanna put the high flows back on, don't really wanna live with that exhaust sound.