H'ville TA

I need your advice. Ever since I installed my headers I have been get a rattle coming through my exhaust in drive - not park. Not a rattle like something touching or loose external to the exhaust, more like a resonating rattle - reminds my of my cousins Silverado Z71 with straight pipes. Not an attractive sound on my TA. My setup is a Pacesetter LT headers, Pacesetter ORY (with a bump stop), into a SLP Loudmouth. I removed the SLP catback and installed the factory catback muffler to verify the Pacesetter dumping into SLP wasn't the problem. Now, the exhaust is more quite but the rattle/resonation still persists @ 1700-3000K while driving. Do we think it could be a bad set of headers (two of the primaries making contact when under load), poor design on the Pacesetter header or ORY, or something else? I have considered replacing the headers but I figured I would ask the forum incase it's something simple or if someone has run into this before.