New Torca clamps on the mufflers? Exhaust sealant at the joints? Proper torque and new gaskets at the exhaust ports?

If you're completely positive it's not an exhaust leak, then start working on the tune.

 

On my stock 103 ci RKC I had poping. Last week I got out the service manual. Found the torque. Took the header bolts to max torque. Poping almost completely gone.

 

My Rineharts TD's do not pop at all so it is not normal.

 

+1 on richening the map at 0 throttle above about 1500 RPM. Not sure how to go about it on the thundermax but on the PC-V its a simple matter of plugging into the computer and changing the values all down the 0 throttle line by +20 ish

I had bad decel popping and that took care of 99% of it