The one in the set [and the above pic] is a very thin rubber... [may not look it in the pic but it is...]

 

I've bought the kit with the thin rubber gasket, pictured above. It is very thin, very flexible rubber, not a semi-rigid gasket material.

Are you aware that the top of the throttle body, where that cover sits is not subjected to any appreciable vacuum? The port is in front of the throttle body, so it only sees a tiny amount of vacuum at WOT. That chamber normally flows air OUT of the TB, to the passenger side valve cover. From there the air is pulled through the crankcase and the lifter valley, and out through the PCV valve, subjected to a limited vacuum.

You will not see much vacuum of any sort, and not enough to pull the rubber gasket down.

It is no more than a gasket to insure that air does not leak in through the edges of the cover plate.

 

Ok thanks for the explanation on that.

Yeah as for the flow direction, I know it's supposed to flow the other way but oil in the area where the pcv hose feeds in from the valve cover indicates otherwise, or is it oil that simply hasn't left the throttle body from the pcv valve side yet? 112k on the motor - I figured I have a little pressure loss or whatever causing it to flow backwards from time to time... you could explain that better than me as well.

I don't have the plate off right now but I guess I'll see what you're talking about when I take it back off to put the mentioned gasket in. Seems like if there's enough passage for the oil to get through either way, then there'd be enough to let a vacuum build as air comes in thru the elbow and into the chamber. Guess I'll have to wait till I take it apart to see what you're talking about. I don't have a detailed enough memory of it.

 

at high throttle/WOT, there is no vacuum through the PCV valve, so all blow-by gases are being sent back through that hose