Just finished taking mine out! Funny story actually.... a couple years ago I noticed a low pitched rumble during acceleration (it wasn't there if I was just cruising, but when starting from a dead stop or increasing speed, I would hear it). I never did anything about it because it wasn't bothering me that much. Well today as I took out the resonator, I noticed it had a chunk taken out of it, i guess from some debris or something. So I figure thats what was causing the rumble (which is now louder Hopefully I'll upgrade to a real CAI someday.....