You need to rule out fuel , if you can put a gauge on, pas side fuel rail there is a schrader valve, pressure should be 35-45 psi key on engine off 30-40 running , if you cant , kleen flow air intake system cleaner aerosol , spray into air intake lightly & if rpm comes up it is a fuel delivery problem ( lean )we used to replace a lot of fuel pressure regulators on that system. tranny shifting problems will occur if an engine has lack of power.If every thing checks out here I would head to the distributer. But a good scanner ( snapon ) would be a good place to start, A decent garage, I know we do , will stop by with scanner for a small fee & scan system for you,