  In this paper we analyze the steady state of the Asymmetric Simple Exclusion
process with open boundaries and second class particles by deforming it through
the introduction of spectral parameters. The (unnormalized) probabilities of
the particle configurations get promoted to Laurent polynomials in the spectral
parameters and are constructed in terms of non-symmetric Koornwinder
polynomials. In particular we show that the partition function coincides with a
symmetric Macdonald-Koornwinder polynomial. As an outcome we compute the steady
current and the average density of first class particles.
