@gamemaster
i had the same problem on ma platz, and to be honest i think i still have the same problem. why ? because it only happened to ma car in summers when the AC was on. there was no problem of backfiring or the spark plug gap adjustment, still it kept on doin so. i have even posted the pics of ma filter in the topic i made for the exact same issue. search and u wud find it. still, if u have found a cure to it , wud u please like to share
thankz