What causes backfire through air flow system on 1990 Pontiac Bonneville

changed mass air flow and crank sensor won't stay running any more tried catalytic converter didnt work

1 answer 1 comment
TAKE IT IN AND HAVE IT DIAG BY A MECH YOU ARE WASTING $
alright i figured as much my wife has been sayin the same thing but its no fun listening to her that would be to easy lol