i have just put on a back box on my exhaust up to the cat ,buy i have a noise now like boiling water, when the car is idling i dont think i damaged the cat,buy could have if its very delicate,is the cat the flexable piece of tubing i can see

nope that is not the cat that is just a felible jpoint to allow for movement of engien block. the cat is encased in metal surround and normally looks like another small barrel well sort of lol. ie large then normal exhaust piupe.

dont know about mk1 punto but if you have a mk2 the cat is directly attched to the manifold before it bends under the sump. (excepy hgt's i think)

on a side not i recntly changed the same as you and my one has a sttrang nouse to it.

The boiling noise is nothing to worry about if its the same noise i had.

had a mechanic look at it. he said it was nothing to worry about. forgot wat he said it was.

the cat looks like a large rusty cylinder that lives between the footwells on a mk1

Mk1 cats are seperate to the downpipe

thanks for the replies guys, i found the problem,i moved the exhaust 1/2 to the side, i would not have believed the horrible noise was caused by this , thanks anyway