catback loss of power
 

I've got a lot of blowing and vibration coming from the catback and lack of power passed 5k .
Am I right in thinking if the exhaust system is leaking gases the car will suffer power loss.

An exhaust leak after the front O2 sensor will not typically affect power levels dramatically. Technically it can, but from a disrupted exhaust flow perspective, so it wouldn't affect it more than changing between various exhaust designs would affect power.

The typical problem with our exhausts as they relate to high RPM power loss is a clogged cat. It could be a number of other things as well, not related to the exhaust.