Truck Repair: chev truck heater, rubber reducer, vacuum leak

Question
my 1990 chev 2wd 1500 has poor heat.when i rev the engine the heat becomes hotter.it has a 305 engine.the heater controlls seem to work fine.I have just replaced the metal water pipe that is on the intake manifold located at the rear of the engine and hooks up to the heater core.(the rubber reducer was swollen shut preventing any water from flowing to heater core)I have removed the fan and cleaned the debree from in front of the heater core.could this be an air lock in the system?is the system run on vacuum thus creating a vacuum leak preventing the temp from increasing?also my air cond is fully charged yet i have no cold air.any idea what could be causing these problems?is this more than a single problem or seperate problems? thanks

Answer
Probably separate problems.
Remove both hoses from the heater core, and run some water from a garden hose through it. Switch directions several times.
I have heard Dex-Cool blamed for plugging them. Search on Google.com for Dexcool links.

Good luck,
Van