Ok..on the lower manifold of the EFi 5L thers a bafle underneath where the PCV valve sits in...what happens if you dont install this baffle..???

Came across the same thing when i swapped my HO manifold to a Explorer, I just fitted the rubber grommet and installed the valve.
Don't know if there is any disadvantage, but have had no probs so far with my motor.

well i took the manifold off and fitted the bafle...i took the plenum cover off the manifold and there was a pool of oil in there......and my plugs fowled up big time after bout 25 kms of driving...

Ive got a cobra intake manifold,came straight from the states to the engine rebuilder so I dont know if mine has a baffle.Aked Vic cause he has the same manifold as me and his has a small baffle.I found small amounts of oil in the intake when removing the top section so I made up a catch can that hooks up to the hose comming from the PCV valve and then goes into the intake.Ive also had trouble with plugs fouling before I did this.Every service I empty the catch can and get about 600mls of oil.

so you put like a t-piece in the pcv valve house and connect the catch can to that ???

I think if you used a t-piece the oil would still be sucked through.Best idea is to use a larger baffle to stop oil splash being sucked into the PCV valve.The catch can I made up has a gas tight cap and two fittings into it,one for in and one for out.The good thing about having a screew lid its easy to check how high the oil level is getting so that you dont suck a heap of oil into the motor.I glued a ceramic block to the side of the can and ground a groove in it then it clamps to the dipstick for easy access and removal to empty the oil out.I went with the catch can idea cause it was a lot easier than removing the intake and having to get new gaskets.

well i put the baffle in..and i also bought a catch can the same as yours...hose in, hose out, screw lid on top with o-ring seal, & drain plug at the bottom..