Trouble hooking up and H pipe 69 mustang

[tredd1]

Hi

I just got a duel exhaust for my 69 mustang. I went to start it up tonight and it sounded like I didnt have the exhaust on it. I think I pout it together correctly. I used a felpro manifold gasket kit. I put the donut in first then a flat gasket then tightened it all down. Just doesnt sound right. Did I but the gaskets in right? any suggestions??
Thanks