Toyota Repair: Toyota intake manifold, allen bolt, head gasket

Question
My truck is a 1990 Toyota 4x4 extended cab pickup. Standard, 4 cylinder.
The head gasket is blown or the head is cracked. I'm trying to remove the
head to take it to a shop for testing and other work. Everything is off except
the intake manifold. It won't move. I have removed all the nuts as far as I can
see. I am reluctant to apply too much force to it as I don't want to crack the
manifold. What am I missing?  Note: the fuel system is still pressurized. truck
was not running to turn over to depressurize. Should it not be possible to
separate intake from head without depressurizing system?  

Answer
The fuel system has nothing to do with it, you are missing a bolt that is still in the manifold towards the front is a long 6mm allen bolt it goes all the way through into the head, remove it and the manifold comes off, if you can't find it let me know and I can send an illustration, I know that follow ups through this site can be difficult so contact me directly at tedrttr@yahoo.com if necessary.