The mummies found in the Tarim Basin were not wearing kilts. (Celtic like fabrics, yes) Read the book The Mummies Of Urumchi by Elizabeth Barber, a textile expert. One thing peculiar about the clothing worn by the mummies is that they were exactly the same as those found at the famous Celtic sites at Hallstadt. The material, patterns and manufacturing techniques were exactly the same.
It is my theory that the people found out there in the desert were refugees from the 5,600BC flood of the Black Sea...and they spoke Tocharian A & B.