2fast2lexury

Hey , i'm bew to these forums but i was wondering if someone could answer this. My lexus was once quiet as a mouse, now its loud as if there's a hole in the exhaust somewhere . However , sometimes the car shakes in a back and forth motion while driving, ive changed the spark plugs and coils was fine , i was wondering should i get a whole new exhaust or is it my catalytic converter all stopped up , or flex pipe needing replacing ?.