Had LTE dual exhaust, swapped back to factory exhaust (S header) instead of the ole Y that is notorious for rusting out.

Took out spark arrestor and started backfiring.
Note it has UTV Inc intake with 2" snorkels.
Factory ECU.
TPS within specs (checked recently)
Iridium plugs.
It’s a 2008.

Never backfired with the LTE duals until now?
All the seals on factory exhaust looked ok. Didn’t feel any leaks but it was too warm for me to keep may hands and arms around the possible areas to leak.

Any help or ideas would be great!

Possible exhaust leak?
What is the average temp the jug, headers, muffler should be after warm?