But to answer the question as I read it this time: oil pressure will decrease very little if any. Flow will increase due to the larger line, quality gauge would do wonders in reading proper pressure.
If the oil goes through the remote line before going into the engine, then a narrower line will most likely decrease pressure. I will act as a restriction to the pump. Oil pressure is (and should be) determined by the oil pump, oil, and internal engine clearances.