So do I just need to buy a downpipe as a replacement?

Hey I’m new to these forms! I have a 2006 Volvo V50 T5 Awd wagon and I have a muffler and resonator delete on the car. If I pat the gas around 2500 rpms the car wants to pop off and kind of back fire. Considering I have the cat, the car turns red and starts smelling :lol: I think it’s time for me to...