1600 tp with webber progressive Back fire on over run

[spanneredmonkey]

Ok with my battle to make my van more drivable I have sorted the binding brakes and the vauge steering, now I have noticed that I have a back fire on over run when decellerating, I have a feeling that I am over fueling and thats whats causing it, though I am after some advice on what to look at first, I have checked the timing and its bob on.
Its a 1600 TP with a webber progressive carb and a 009 dizzy, other than the pop and bang on deceleration the engine runs well and pulls fine,

 

[67westy]

Exhaust leak as I was told when I had a similar problem

 

[spanneredmonkey]

ahhhhhhh that makes sense..Thanks .. I noiced a bit of soot on the flange between the header and box... will get that sorted!