The same thing has just happened to my wife!
And this post has sort of steered me in the right direction. Is there anything lse you would suggest thats not been mentioned?
I have a 2009 corolla professional, 370000km on the clock 14km/l. Replaced the muffler with a freeflow box and removed the resonator, beside the car being loud, My fuel consumption now is 11km/l but way better performance, considering to have the catalytic converter removed. Any advice?