Fuel in oil

I have a 1994 4.0 Ranger that is getting fuel in the crankcase. On occasion it misfires and blows the vacuum hose off the upper air intake vacuum connector. These vacuum lines have become sloppy due to what I believe to be fuel entering them. I have checked the fuel regulator pressure and the readings seem to be normal. Key on engine off only gets up to pressue if I engage it a couple times. It will hold pressure for some time before it starts to taper off. Haynes says to pinch off the return line and you should see no increase in pressure. This doesnt sound right. When I pinch off the return line I see a significant increase in pressure. When I remove the vacuum from the regulator the pressure goes up and when it is applied it goes down. All this seems to function as has been described by the manual except the initial koeo reading and the pinch off of the return. Any help would be appreciated.

check ignition timing and look for a leaky injector. I'd start by checking plugs they'll tell you whats going on in the combustion chambers(running rich, lean,etc.)
Remove oil dipstick do you feel any "excess" pressure coming out? Excess blow by through the piston rings would cause fuel in the oil.
Have you changed your PCV?

Thanks Carlos80. I have checked the plugs and one the number 5 plug had excessive carbon buildup and appeared wet. All the plugs on that side had excessive electrode wear(Motorcraft Platinum) the other side looked good. I havent changed out the PCV it doesnt appear to be clogged or stuck. Should I change it? Would pinching off the return gas line cause an increase in pressure if the regulator is functioning? My haynes manual says that it should not increase and that if it does replace the regulator.

In my opinion pressure would increase, the fuel has to go somewhere any restriction would cause pressure to build up. Sounds like 5 s running a little rich. Pressurize the fuel system then try and block the rail in(both return and supply line) pressure should hold for at least a couple of hours if it drops considerably then you could have a leaky injector. I like to clean the plugs before doing this test then remove them to see if they're wet. If you suspect a cyl then make sure the valves are open to allow the fuel into the combustion chamber, and the engine is not hot. Another sing of a leaky injector is black smoke on start up, then it clears out.
You might want to run some injector cleaner through the tank. I would change the PCV its inexpensive and can actually cause a lot of problems.