Well, I suppose this is sort of tech-related but figured I'd be more likely to get an answer here than in a tech-specific forum. Here goes....Just had a Flowmaster 40 series installed on my 05 V6. Gives it a geat tone and it's a lot of fun to gun the engine in parking garages. However, there is an occasional "rattle" kind of sound coming from the muffler. Nothing is loose and the guys that installed it did a great job. Pounding on the muffler and other parts proves nothing and the sound appears to come and go with no rhyme or reason. The best way I can describe it is that it sort of (emphasis on "sort of") sounds like that rattle you get in an engine that needs a tune-up or better gas). As far as I can tell there's no relation to speed, RPMs or whatever. It's not an overpowering noise by any means but a little annoying that it comes and goes at will. Insight or advice anyone? Thanks in advance!