Thanks for your help.
Have a clean K&N filter and popping is much less than before. Will check intake headers and remove the 6deg TW. Will post the result.
A thought.....did you remove both rubber gaskets from the air box and lid? If not the K&N filter cannot seat itself in that groove and let the air box seal like its supposed to.
I also second the possibility of exhaust header leaks and or intake runner top and bottom clamps loose.
Good luck