Well you say restrict the flow I say enhance the flow. A smooth surface inside the intake
will cause friction and the effect is as if you have a smaller tube to go through. Careful
turbulence enhancement can create more flow. I've used this type of device on my old
Super Sherpa to good effect;
http://www.latus-harley-davidson.com/Turbulator-for-2-Bolt---1-7-8----48mm-Manifolds--S---S-B--Shorty-E--8761.htm?utm_source=google&utm_medium=shopping&utm_term=free&utm_content=Round1&utm_campaign=Googeshoppingfeed&gclid=COmpxezVkbgCFQui4AoddkgA_A
So a little bit of RTV might be a good thing!
I know that air aswell as any liquid will grab on to any surface and some of the air will almost be standing still no matter how high the air velocity in the center is, but anything that for a short distance decreases the diameter will have a bad effect on both flow and pressure waves.
The effect from flow is that the air needs to be at higher speed when going through a tube of smaller diameter, and because of the airs inertia, a pressure drop will occour from one side of the restriction to the other. Also, if the restriction has not got uniform and smooth surfaces, turbulence will be created and energy will once again be lost.
The effect on pressure waves is greatest if the restriction in the air path is not perfectly round, as the waves will be bounced in different directions. Also, if the diameter is decreased by more than one third, it will make a pressure wave with the same sign as the original pressure wave. This mean that when the intake opens and the negative pressure wave travels up the intake, it will hit the restriction and turn around, sucking air out of the cylinder. :p
Anyway, what i experienced with having silicone as a sealant between the cylinder head and the black spacer was that the silicone was pushed out into the intake in an all but uniform shape.
I can not in my current slightly intoxicated state visualise what the device you used would do to the air stream but sending it swirling around, so i cannot deny that it could reduce what air is trapped at the walls, byt i highly disagree that a smooth surface will trap more air than a rough surface.