207 Exhaust Explosion

I have 207 vehicles 1.4 I have an exhaust explosion problem, the exhaust explodes with very low noise but it is heard, for example it bursts when throwing it from 1 to 2 or it explodes while pulling the gas off the gas. What is the reason.

I said there was a catalytic converter error I could have changed it, I changed the interior of the catalyst again

The guy said, "Make that sound," he said. "Does anyone have any knowledge? Well, forums."