I'm not sure how well vetted a certain Dave Gentile's analysis is. But I found on line a statistical survey of certain characteristics of the original Koine Greek in
A) the Q passages in Matthew,
B) the Q passages in Luke,
C) the non-Q passages in Matthew, and
D) the non-Q passages in Luke.
Gentile appears to have come up with a set of "family resemblances" between the Q versions found in both Matthew and Luke and the non-Q passages in Matthew. What this might suggest is that there is a stubborn layer of Matthew characteristics that is left intact in both Q versions, both in Matthew and in Luke. One can argue that this may indicate that Luke's Q passages were in fact taken from Matthew (since non-Q passages in Luke seem to bear very little resemblances to Q versions in either Matt. or Luke), rather than an independent source, thereby possibly removing the need for any texts in addition to Matthew and Luke.
However, it could be that the statistical analysis Gentile has given us is totally bogus, and both Q versions still have earmarks of a style wholly foreign to both the non-Q passages in Matthew and the non-Q passages in Luke. It's hard to know how sound this Gentile analysis is without consulting someone like Ehrman or Crossan or someone of that stature.
Anyway, here it is --
http://www.davegentile.com/synoptics/main.html
-- and I've tried many a time, via relatively reputable scholarship forums like Crosstalk, etc., to get some kind of gauge from someone knowledgeable as to the probity of this analysis. So far, no luck. But obviously, the questions raised by the Gentile statistics -- if valid -- do put the notion of any separate Q source -- whether written or even just oral -- in some question.
Stone