I placed down 2 strong boxes with an impulse item duct in between them with a servo set to disabled and stack size of 64. I filled the "sending" strong box with full stacks of leadstone energy conduits. I let all of the items arrive into the receiving box then filled the sending box back up. Does not really matter the item as they all react the same whether it is vanilla blocks or TE items. Now you would be thinking with a single impulse item duct and this being 100% TE that the communication of this "stuffed" scenario would not have a problem, but sure enough TE duct system is SOOO hyperactive that in the time that I take half a stack of items from the receiving box and it announcing that it has room for 32 items and the sending box saying, "ok, here have 64" it then sends another 64.
So, you tell your 'input' connection to send a full stack at a time, pull out half a stack, and curse the mod for being dumb when it sends a full stack. This seems illogical to me.
Also, this IS the test platform. There is a reason 2.1.3 is a non-recommended beta update. If you're not willing to be a beta tester, wait for recommended packs!