T5 Mutlivan 2007 Highline 6 speed manual diesel 27,000km

Backfired today and blew the airhose off at the retaining clip. Never done that before.

Retattached ran fine till there was an increase in pressure and then blew it off again. No error/warning lights on dash.

Towed to dealer, 20 days out of warranty but as I'd had it serviced there they seemed okish re just out of warranty issue. 24-48 hours to look at it.

Any ideas as to why this would happen?

Plenty of diesel in the tank and I do long enough trips every day to get everyting fully warmed up, although this happened before it was fully warm.

Cheers