Suspicious Latin thread of variants

As some of you know, I've developed a certain suspicion towards a number of text-critical notes that use early translations of the NT to support certain Greek readings. Obviously there are many examples of good notes, but in all the major versional languages (Coptic, Latin, and Syriac) there seem to be notes that are not really justified.

This afternoon I decided to take a trawl through the first chapter of John in NA27 looking at the Old Latin. I note that in 1:17, 26, and 42 Old Latin witnesses reading autem are cited in support of δε, and that in the former two of these cases the reading with δε does not have wide Greek support.

The data from within this chapter suggest that it is rather precarious to infer that behind an Old Latin autem there must necessarily be a Greek δε. See 1:35 and, to a lesser extent, 1:40 and 47. Does anyone fancy doing the leg-work throughout all the Gospels to try to get a sense of the extent of correspondence between autem and δε and, consequently, the degree of confidence that can be ascribed to such textual notes?

I don't know whether there has been any study of autem in the Latin. I would, however, draw attention to a sentence in Philip Burton, The Old Latin Gospels: A Study of Their Texts and Language (Oxford, 2000), p. 91: 'Thus the humble δε, though almost lexically empty, may be rendered as et, autem, or vero, according as it marks simple continuity, slight, or strong antithesis.'