454 dually vapor locking ideas?

[chris mc bride]

My lil brother called me tonight about his dually vapor locking and asked for any cures. He has already changed pump,new edelbrock carb,2 inche spacer and reroutes fuel line. Hes getting ready to install headers and true dual exhast,trying to get better milage and maybe help getting heat out of motor.
I've had tons expreiance tuning race car engines,but street stuff not my specaility.Only had few vehicles with this problem and nver realy found a good cure. Figure maybe some og you guys might have idea.