Blowing Decat

Does anyone have any tips for fitting a decat pipe?

My one is blowing quite bad and I'm pretty suprised. Fitted it first time and have since tried to sort it. Used one of these sleeves http://www.ebay.co.uk/itm/1-75-45mm...eeve-Joiner-/221664233908?hash=item339c37c9b4 (Just an example not this one) Used plenty of exhaust paste, tightened the clamp as tight as I possibly can and its still blowing from the joint and it sounds terrible. Dry fitting - the sleeve was a good fit for the flexi and exhaust.

I've used these sleeves before on other cars and they have sealed well.
 
Try high temp silicone instead of exhaust paste. Used it successfully on my old 182 as they are known to blow at the olive joint in the same place.