backfire

My 92 960 wagon backfired while starting. It blew off all 6 of the
intake manifold connection boots, and left the intake manifold itself
tilted about 2 inches to the driver's side.
Repair at the side of the road took about 2 hours and involved
pulling the fuel injection rail, the injectors, and fighting the boots
back into place. I plan to replace the boots and clamps.
Question is.......why did this happen? Is there a connection to
hold the manifold in place, other than the boots? And why the
backfire.........that's a first.

 

Don't touch the gas pedal while cranking...
Can't say about Volvo,s specifically but it's guaranteed to blow the air
box off girlfriendzilla's Jeep if I step on the gas while turning it over.