I do seem to remember one service formed of just a 2-car Turbo in 2015, though whether that was a normal formation I don't know. It departed Paddington at xx12 or xx42 (would have been 1712, 1742 or 1812, presumably). I think it went non-stop to Maidenhead, which would have presumably cut down demand due to not serving intermediate stations, possibly allowing a 2-car to be sufficient.
The BR Coaching Stock group on groups.io has full Paddington CWNs for 1981, 1985 and 1989 (and thus nicely gives a good idea of patterns throughout the 80s!)
Focusing on evening workings only: in 1981 there was a 1641, calling at Ealing, Slough and all, formed of a 3-car DMU (presumably a 117). It's odd that the one through service was before 1700.
In 1985 I can't see any through evening workings, nor in 1989. That said, in 1989 there was a 1751 loco-hauled "Maidenhead Express" calling at Slough only before terminating at Maidenhead, which provided a connection. Perhaps in the mid-late 80s it was deemed better to provide connections off fast main-line loco-hauled services rather than try and run a through slow service with slower 117s.
More recently, I have the 2008 timetable and that shows a 1744 and 1844 to Bourne End, calling at Slough only before Maidenhead. Incidentally there was also a 1714 and 1814 to Henley, calling at Slough, Maidenhead and Twyford, so both branches got through services that year.
