Your experiments are interesting, I commend your diligence (200 runs) and your scientific approach. My comments on your graphs for Dpf soot build-up at a 50 mph journey and an 80/90 mph journey. Please note during the Euro emissions tests the vehicle Is driven mainly in the 30 to 50 mph range...

To split the welds on the cat dpf etc, it will very likely to be a hydraulic in cause, not air or exhaust gas .Hydraulic such as water or the "white stuff" liquid, liquids are incompresible in volume and generate high pressure on the containing vessel. Air or exhaust gas I believe would simply...