Its a long story, but basically I accidently let my engine rev to about 7.1 rpm even though it redlines at 6.8 rpm. i didnt think i did any damage, since the computer should have a rev limiter, but since then my engine sounds weird. it makes this kinda fuzzy noise, and it sounds like there is more noise comming from the engine compartment. i put on a cat back about a month ago, so there had been a deep grumble comming from the rear of the car, now there is a fuzzy sound comming from the front of that car. any ideas what might have happened? could i have done any physical damage, or is it all in my head?