  Two Jovian-sized planets are orbiting the star HD155358 near exact mean
motion resonance (MMR) commensurability. In this work we re-analyze the radial
velocity (RV) data previously collected by Robertson et al. (2012). Using a
Bayesian framework we construct two models - one that includes and one that
excludes gravitational planet-planet interactions (PPI). We find that the
orbital parameters from our PPI and noPPI models differ by up to $2\sigma$,
with our noPPI model being statistically consistent with previous results. In
addition, our new PPI model strongly favours the planets being in MMR while our
noPPI model strongly disfavours MMR. We conduct a stability analysis by drawing
samples from our PPI model's posterior distribution and simulating them for
$10^9$ years, finding that our best-fit values land firmly in a stable region
of parameter space.
  We explore a series of formation models that migrate the planets into their
observed MMR. We then use these models to directly fit to the observed RV data,
where each model is uniquely parameterized by only three constants describing
its migration history. Using a Bayesian framework we find that a number of
migration models fit the RV data surprisingly well, with some migration
parameters being ruled out.
  Our analysis shows that planet-planet interactions are important to take into
account when modelling observations of multi-planetary systems. The additional
information that one can gain from interacting models can help constrain planet
migration parameters.
