Engine back pressure question (help) please?

Okay I have a full cat-back exhaust system headers to muffler.. But my catalytic converter is gutted (was already before I put the exhaust system on) .. so basically its a straight pipe from the header to the muffler. My question though is I don't think I'm getting any back pressure and losing HP when I press the gas (not flooring) it feels like your accelerating from like 3rd gear or something. So I got another catalytic converter, should I put it on and will it help me gain lost power?