everytime i put a pod on, my car backfires, not loud, really quietly and every few minutes depending on gear etc, like when i change down a gear..

then when i take it off, its fine and runs beautifully. its odd because all the pod does it filter air so im baffled.. any ideas? iv tried a couple, this one is just a cheapo one and its the one that backfires the least, also once i have one on, it doesnt run as smooth anymore.

u guys all know a heap more than me so i hope you get what i mean?

(theres no other mods apart from exhaust as i was gonna sell it but changed my mind so the pod was the first thing to go back on, yes i need a tune but thats not the issue)