Usually a poorly tuned engine or clogged air filter will lead to excessive unburned fuel in the cylinder then it leaks down past the rings into the oil crankcase. Try a new set of spark plugs, distributor cap and rotor and a new air filter.
check your fuel pressure. there is a port on the back of the intake on the drivers side with a plastic cap on it(looks like a valve stem cap). you may have a bad fuel pressure regulator. you can get the regulator at your local part store. You DO NOT have to replace the whole spider injector to fix it. if you have the vortec engine this is a common problem. Your fuel pressure should be 55-61 psi if the pressure drops as soon as you shut the key off you have a fuel leak. It should bleed down to about 50psi or so and stay there. you can activate the fuel pump under the hood with out the key on. there is a pump prime port in the engine bay. It comes out under the distribution block on the firewall it is a single wire that is sticking out of the harness, the wire should be gray in color it goes straight to the feul pump, use a fused jumper wire fron the pump prime port to the battery to activate the pump. more than likely it is the FPR, Hope this helps