I installed my Megan headers w/o cat at about 4K miles on my 09 tC, Im now at about 5K Miles. At first it just had the normal rasp. I then started hearing a rattle at certain RPM's after about 300 miles of it installed. It has since gotten worse and now sounds horrible. Ive made sure that all of the bolts were tight and everything was lined up correctly, all of the gaskets are in place also. I will be taking off my header this weekend to try and troubleshoot the issue. Any information, suggestions, or help is greatly appreciated. Thank You!!!!

 

Might be a crack on the bottom collector, I have mine on for about 3 years before I replaced it with a DME one and when I looked at it carefully the weld at the bottom of the collector was cracked, that might not be it, but might be worth looking into it, good luck thou.

 

FIXED!!! Well I couldnt wait till Sunday to work on my car so I got out the floor jack and jack stands and started looking around. I looked for the crack in the weld first and everything looked A-OK. Well it turned out to be my anti-foulers (fix for CEL) there was a locking ring in between the two anti-foulers and it busted! the 02 sensor and second anti fouler was rattling all over the place i was lucky i did not damage the o2 sensor. So I got out some high-temp teflon tape and wrapped the anti-fouler in it and screwed it all back togeth. BAM! No more rattle! TIP when using anti-foulers id get rid of the locking ring and get some high-temp teflon tape or lock-tight. Also make sure your you unplug your o2 sensor so when you screw it in there isnt any tension to possible unscrew the o2 sensor or cause damage.