  Particle and photon production is analyzed in the presence of transverse flow
using two approximations to describe the properties of the hadronic medium, one
containing only $\pi, \rho, \omega$, and $\eta$ mesons (simplified equation of
state) and the other containing hadrons and resonances from the particle data
table. Both are considered with and without initial quark gluon plasma
formation. In each case the initial temperature is fixed by requiring
$dN_{ch}/dy \sim$ 550 in the final state. It is shown that most observables are
very sensitive to the equation of state. This is particularly evident when
comparing the results of the simplified equation of state in the scenarios with
and without phase transition. The hadronic gas scenario leads to a
substantially higher rate for the $p_T$-distribution of all particles. In the
complete equation of state with several hundreds of hadronic resonances, the
difference between the scenarios with and without phase transition is rather
modest. Both photon and particle spectra, in a wide $p_T$ range, show very
similar behavior. It is therefore concluded that from the $p_T$ spectra it will
be hard to disentangle quark gluon plasma formation in the initial state. It is
to be stressed however, that there are conceptual difficulties in applying a
pure hadronic gas equation of state at SPS-energies. The phase transition
scenario with a quark gluon plasma present in the initial state seems to be the
more natural one.
