JBCOBRA FI systems donot backfire if setup right. The filter base helps bend the air into the 1,200 cfm throttle body. If you sucked a filter into the carb, you could have had a couple of problems to cause this, possible too dirty, fuel inversion ate the foam, backfires. They tell you to clean and or change the filter every 2-3 years. it does get hard over the years. I like it because it keeps the big junk out of the throttle body and allows the air from the hood scoop to go directly into the throttlebody with out any bending. I don't
oil this foam either. Rick l.