leaks with new Exhaust

i gota leak around where i put a new cat at where it meets the y pipe it leaks along the top an some on the bottom an a lil in the back. what can i use to seal this up?

I used aluminum foil and band clamps. I folded it enough times that it was thick enough to hold up.

you could have it welded....

ya i can have it welded but if i need to get it off i cant unless i cut all the welds an dnt really wanna do that

What kind of system are we talking about here?

i have an off road pipe that i swap out with the cat converter when emissions are due. The pipe and cat have flanges and bolt holes so i can swap it out fairly quickly. If you have this type of connection, you can buy gaskets for it or you can use a RTV high temp silicone sealant.