I don't believe so. The plot card states, I believe-recalling from memory, that Louis can gain 1 good baggage when he sacrifices a lead when following up a lead. It doesn't say that he can sacrifice when "placing a lead", "placing evidence", "uncovering the conspiracy", or other simliar terms.
That would indicate, in my opinon, that in the act of following up the lead he would decide to sacrifice the lead he obtained before resolution of the Follow Up action. In other words, Louis pays the 1 time to Follow Up The Lead, picks up the lead token and hands it to the player on the left to place in a new location(before the last 2 days, of course), and before he makes the decsion on how to use the lead he declares that he is sacrificing the lead for baggage.
Allowing Louis to "peek" at the evidence or puzzle piece beforehand would not be a sacrifice if he can just "discard" pieces he doesn't want for baggage.
In the same vein, if Louis has any cards that allow him to place a second peice of evidence after the first, these can also not be used to add good baggage, in my opinion. This is because the act of following up the lead has already taken place, or was skipped entirely, and Louis is already advanced to the "placing evidence" stage.
In the games I have played so far, we have seen some confusion in the conceptual difference between a "Lead" and "Evidence". This stems, in my opinion, from the fact that the phrase "placing evidence" in the rule book is occasionally replaced with "placing a lead" on some of Raymond's and Louis's cards. Not sure if it is any other, as they are the only 2 detectives I have played so far. So the need to be precise in the explanation to new players is a must. But this game is so deep and intimidating (or so I have been told by a couple of players) that it takes them a turn or four before they begin to get the hang of it.
Anyway, hope that helps.