2001 gmc sierra 2500hd diesel. Left garage after oil filter change went about 5 miles engine started to bog & smoke bad. Couldn't go more than 5 miles/hr. after checking under hood noticed long blue hose to turbo caving in on itself. After undoing short blue hose on other side of turbo engine ran fine - starving for air, cld you explain why & what I should do. Mechanic is not expert on diesel. Thanks Any info wld be appreciated.