Splitting the spectral flow and the SU(3) Casson invariant for spliced   sums
  We show that the SU(3) Casson invariant for spliced sums along certain torus knots equals 16 times the product of their SU(2) Casson knot invariants. The key step is a splitting formula for su(n) spectral flow for closed 3-manifolds split along a torus. 
Hans U. Boden, Benjamin Himpel