yes change the Tstat, the motor will continue to run rich until you do. have you pulled the vacum line on top of the FPR to see if gas is present? if no gas is present in the vacum line then get a Fuel pressure gauge and see what you have. anything above 42psi is to much and anything below 35psi is not enough. if the pressure comes up and then bleeds off quickly then you more than likely have an injector stuck open, you then begin pulling plugs until you find the one with raw fuel. if the pressure is hi the FPR is bad and needs replaced.