I had the same problem with my Specialty Spares after installing and changing to the 130s. I took it back to the installing dealer who then changed the pilots to 45s and the backfiring and loud popping disappeared. I have some decel rumble now and feel that trying to eliminate all decel popping encourages people to turn the screws out to where they are actually running too rich. With a more open exhaust, some low decel popping should occur and is normal.
