Magnaflow CBE and Clunking Noise?

I've had my Magnaflow cat-back exhaust on for a couple months now and in the past few days I've noticed an odd (and inconsistent) clunking noise when going over speed bumps or really rough pavement. The other weekend I just jacked the car up and tightened all the bolts for the cat-back and it doesn't seem to have much give. Is it possible that something on the car is coming in contact with the exhaust or could it be something else entirely causing the noise?

do you have an aftermarket RSB or endlinks?

do you have an aftermarket RSB or endlinks?

 

Nope, completely stock (except for the Magnaflows) '09 Legacy GT with about 3,400 miles on the clock.

i just finished installing my magnaflow cbe (literally... about 30 minutes ago) and i noticed during the install that the center pipe rubbed up against the exhaust heat shield. sure enough on the test drive, there was a little bit of a *clunk* right where the pipe hits the shield. it's pretty flimsy so i was able to bend it out of the way a little but there's still an occasional clunk. i'm gonna take the heat shield off tomorrow and bend it some more.

my suspicions were confirmed. the heat shield has a couple "flared" spots where it rests against the transmission crossmember, and those bulges were butting up against the exhaust. i unbolted one side of the heat shield and pulled it over a bit, then rebolted. as far as the bulges, i had my car up on ramps in a parking lot where you're not really supposed to work on cars, so i needed a quick fix. i took the jack that came with the car and jacked it up against the bulges to push them back a bit. no more metallic clunk!