Hola,
I'm new to working on cars, but I think the problem is probably that you have to heat the intake manifold somehow.. If you don't heat it, the fuel will condense on the walls of the intake insted of going into the cylinders. The stock exhaust manifold has a pipe with a special valve that heats up the bottom of the intake manifold when the engine is cold, if you have headers installed then you don't have this heater anymore and you have to find some other way of heating the intake.
I'm assuming you have the stock intake manifold..
I think langdon's stovebolt sells a kit that you bolt to the bottom of the stock manifold to heat it with the heater water..
Also, I think offy intakes have water heating built in so yeah, the problem probably would be solved with the new manifold, if you install the water heat lines..
Somebody correct me if I'm way off..
