set up:
d16a6/z6 mini me, aprox 35k miles on it
aem intake tubing (2.5" i think), b18a throttle body, skunk2 intake manifold, ebay header, stock cat, oem sir exhaust, chipped p28
symptoms:

recently my engine noise has gone from smooth through out the rpms to very choppy and raspy,
anything above part throttle and the intake noise just gets louder but if anything the car slows down?
the flange gasket on my header between the collector and the down pipe recently blew out, and the replacement sounds like i'm still leaking from that same joint.

car will rev "ok" to about where vtec is supposed to come in then the rpms seem to slow down but the engine noise keeps getting louder and i hear what sounds like a waste gate opening, or a large his

occasionally when i rev the engine at idle i hear a rattling in my exhaust.

went for a cruise tonight, tried to do a pull, made lots of engine noise but barely moved, when i shifted from 1st to 2nd it kind of bogged down for a second before it started to increase rpms again.

mpgs have dropped almost in half

Recent work:
new cap, rotor, plugs, intake manifold gasket, iacv, heater hose, recent oil change.

fluids are full, car reaches full operating temp, recently seems like she developed a large leak from my ps rack so i took the belt off.

not throwing a single code.

any one else suspect my cat is partially clogged?

 

Yes, sounds like the cat could be pluggin' up, which might also explain why your exhaust gasket blew out due to way too much back pressure in the system.

 

^^^ Beat me to it... Your catalytic converter is clogged. If you want to verify this - pull the O2 sensor out of its bung and drive it. If symptoms improve you have your answer.