Resonator size?

Ok so I installed my Apexi WS2 exhaust a few days ago and i didnt get a resonator. Didnt think id need it but i think i do now. Reson i need one is because at high rpms its raspy sound like a civic with stock exhust. During low rpms it sounds great love it its just at high rpms like i said. So far my set up is DC headers, stock cat for now, 2.5 catback to the WS2. Im not sure what size resonator to get or brand. Ill be boosting it in a few months if that makes a diffrence. Please lmk your input thanxx.

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