Exhaust sealant

[dajones]

Fitted a decat to the car a few weeks ago. all running smoothly until recently ive noticed it blowing and also the joint at the rear (car previously had a system then reverted to stock)
I have got around and tightened all the bolts and adjusted the rear sleeve/clamp thing for a better fit but now it needs sealing. I am unsure of what to use. my mate used gungum on there but i have found that its no longer there after cracking off.
Which of these would be best?
Halfords-- Loctite silicone sealant

also i have found that the decat could be a bit too long, Its slid over the pipe and its basically minimum distance from the silencer so i dont think the clamp is actually doing anything as its unable to secure on the standard parts.
so what would be the better option, remove the decat and shorten it. then refit with a sleeve, or would i be better off cutting some "notches" in the end of the decat allowing it to compress around the stock pipe?

Oh everyone loves a paint drawing, this is how it is atm.

 

[martinrs]

Any high temp silicone will do.

Don't use gum gum pastes or the like. What you have linked will be fine

 

[TB Rich]

I just tried the loctite 5920 and its crap imo, perhaps if you use loads and let it cure as suggested for 24hrs it might be ok. But it's very thin and spreads about too much I think.

I took it to the garage and they used a regular paste and apparently now not blowing. would have thought they used a gungum type product?

 

[dajones]

When I get back to work I'm going to find someone local who can take the complete thing off and refit with new sleeves and clamps until sorted out spare money to get a new system

 

[shakey_hand_man]

Silicone sealant is the norm now...

 

[dajones]

It's starting again, I think the clamps fitted are shot. Where can I buy these in a shop on a Saturday? and what size would I need?