Once my car is warmped up and idling or going slow I hear a major clicking noise from under the car.I looked under it but couldent tell where its coming from.Could it be an exhaust leak?
If so,from where? Could the cat be clogged?

 

Get a couple of feet of hose (garden hose, crankcase hose, whatever), put it to your ear and probe around with the other end under the car. You'll hear it better that way, like a stethoscope. If it's an exhaust leak, you'll pick up the pulsations and it will sound different than a rattling. You'll know it right away.

 

If it does it while sitting still and is under the car, it almost has to be an exhaust leak...

 

From where tho?

I got a dynomax catback instaleld a little while ago,could it be from the cat? (its the original cat)

 

Cats can rattle in idle, if the honeycomb is breaking apart. It's like 1 or 2 beans in a coffee can.