I don't know if anyone else has had this problem with the header but if you have a stick watch out for the clutch cable.
The old manifold has some nice heat sheilds on it and the header doesn't.
Anyway, the clutch cable is held together with a plastic cover.  When your off roading and not much air flow is going into the engine compartment, it will (at least mine did with 2 cables) ment the plastic and the cable will come apart.
I fixed mine by winding wire around it from the dash to the front of the engine.  It now looks like I have a spring around it.
Now eventhough the plastic gets hot the cable can't unwine.