This truck has 91000 miles. When it is cold it starts up but runs rough unless it is revved over 2500 RPMs, once it warms up it will not run at all. There is also a very strong vacuum in the crankcase, even when you disconnect the pcv hose. The vacuum is so strong, when you go to put the oil cap back on when the engine is running, it will pull it right out of your hand. My next step is going to be changing the intake gasket but wanted some other guidance so any other ideas?