I have successfully installed a number of shifter cables in different older Shimano levers, where it was usually quite easy to find the channel for the cable. On the current 105 shifters I am stumped - spent an hour in the garage searching for a likely hole or passage way to insert the darn shifter cable, with no luck! Even pushed a cable into the shifter from the other end, along the cable guides, which didn't reveal any possible entry from the front. Where did they hide it this time?
PS.: I was working on the left-hand handle.