I'm running factory exhaust, no mods.aftermarket exhaust?
most aftermarket exhausts allow air into the system at the flange as they can't fully seat into the exhaust port and the acorn nuts bottom out. I installed some 3mm standoff spacers between the flange and the acorn nut to force the flange to fully seat without the acorn bottoming out,
got rid of about 95% of the decel pop, I still get a little pop sound now and again but sounds nothing like what it was.
Lyn-Tron, Aluminum, Metric, M6 Screw Size, 13 millimeters OD, 6.3 millimeters ID, 35 millimeters Length (Pack of 5): Hardware Spacers: Amazon.com: Industrial & Scientific