Ford Repair: wont idle after carb change, performance carburetor, holley performance

Question
My son has a  one ton Ford truck which he and his dad rebuilt 2 years ago. The engine is new and I am not sure of the size.. does 350 sound right? Anyway he wanted to upgrade some parts so bought a Holley performance carburetor and followed the instructions carefully. He also installed new flowmaster headers. But all is not well. Despite following the instructions to a T.. the engine starts, runs fine but will not idle. Several friends/experts have had a look, tried stuff and still nothing worked to solve the problem. Do you have any ideas? We live a long way from town, so towing it in to a repair shop isn't really an option.

Answer
sounds like it might be running to lean or rich-please follow up with following questions and i will try to answer tomorrow night

first when it is running above an idle is it smooth?
do you see any black smoke coming from exhaust?
do you hear/feel any sputtering/spitting or popping or does it just die?

if you see any black smoke it is running rich-(to much gas)and if timing is set right-try to adjust carb and if it won't adjust it may be bad-a carter carb is easier to work on and runs much smoother i know you don't want to hear that but it's true.

if it is not smooth above idle could have engine or timing problem

could be running lean try spraying carb cleaner or even water around base of carb-intake manifold-and around plug wires to see if anything changes.

what area do you live in i might be able to contact someone locally that could give you and idea or two.