If you took that out, your machine is probably running lean. The ecu program is calibrated around 40hp, not 50, and without an o2 sensor it isn't going to compensate. I haven't done this myself, but I'd be interested to know what your plugs look like. If the crew and xp have the same ecu, it can be reprogrammed for an xp. Not sure if anything else is different between the two machines.
There is a trick to reflashing an ecu to a different models program, if you or your dealer need this info, pm me.