Hi guys,
well i ripped the cat out out the dump pipe and fuel economy has returned to normal, still have a bit of a rough idle but the power down has returned and driving great again, im not sure what i would have to do to correct the idle but i am happy that the car is back to normal driving if not better!
only thing i can think of is replacing the o2 sensor. might try that soon.
thanks heaps Scotty!
I hope this cant help other people, and i would recommend getting rid of that constrictive front dump/cat!