You may consider removing the egr tube to clean the restrictor that is in the tube between the two dpfe take offs,if its the 'cat side' that keeps blowing off you may have the start of a blocked/plugged light off cat (too much back pressure).....

V6 MTX
'Don't p**s up my back then tell me it's raining!!!"
'Its only nuts & bolts!'
'If I build it,fix it,upgrade it or modify it...MAYBE they will come....!
Haines Motor Sports Inc,
Dealer for 'Quaife America' & 'Autotech Sport Tuning'
SOLE USA Dealer for the American Axle 'AUSSIE BAR'...
Get a Turbo for you Zetec from HMS Inc...by 'The Demon' ...www.DemonDynamics.co.uk
..don't talk about it DO IT !!!