One thing you can rule out is the fuel pressure regulator. When the diaphragm ruptures, pressurized fuel is sucked up the vacuum line and floods the intake manifold. Check the vacuum line on your fuel pressure regulator and see if it is fuel soaked. I don't see how bad injector o-rings can cause flooding of the crankcase with gas. They seal the injector to the fuel rail on on end and to the intake on the other. If they leak,it is to atmosphere (external), they can not cause a leak across the injector. I'm not saying that they don't need replaced, just that this not likely your flooding problem. When replacing these o-rings, lube them with Vaseline, then gently rock the injector to seat it. Do not twist or rotate, as this type of motion can damage the o-ring.