Cat Plugged??? and pipe size question

[carkhz316]

So, for the last month or so, I noticed what seems to be an exhaust leak emanating from underneath the Monte. (98 z34). It seems to be coming from right underneath firewall, to shortly downstream from there area. It's just a fluttery, light air leak kind of sound, if that makes any sense. And I only hear the leak under acceleration, more noticable when the car is cold. I've noticed that my mileage seems to have decreased and power seems like it's not all there. Pretty sure the cats plugged. Will probably replace it but will just go with a generic one. What is the pipe size in front of and behind the cat? Also, is that resonator immediately behind the cat necessary as I think it might be easier to replace it with pipe. (Or don't do this???) I'll probably be welding it all together, maybe a clamp, but need to know pipe sizes just to be sure. Thanks for lookin!

[Radnsmash]

I think the pipe size on our cars is 2 and a quarter, but does anyone know for sure?

[1990lumina]

I would leave the resonator or put a diffrent one in. The exhaust will be considerably louder without it.

[carkhz316]

Ya, I don't want it any louder. That's why I asked. It's already got the just right tone and volume with my stock mufflers that have holes rusted in them. I guess I could just stick a caliper around to get the measurement or something, but thought I would confer with the enthusiasts first.