Are your cables where they touch the unit bare wire or housing? Probably bare wire, which means the wire is normally under tension. Does the unit deflect the wires and mean that the cable path is slightly longer? If so, your shifter indexing will be affected. That could be compensated for it the path length never changes. But if the cable pushes into or may cut into something on the unit, then the path length may not remain constant and your indexing may act flakey. Besides the cable rubbing may damage the unit or break the cable. So you should be very cautious about installing the unit if it will be touching your shifter cables in normal operation. Moving cable aside during installation is OK.
Oil is good, grease is better.
2007 Peter Mooney w/S&S couplers/Terry Butterfly
1993 Bridgestone MB-3/Avocet O2 Air 40W
1980 Columbus Frame with 1970 Campy parts
1954 Raleigh 3-speed/Brooks B72