carb or fi? I do not think it would be a plugged cat as you state you can run down the hiway with no issues.
when it "dog outs" is it that you are giving gas and it is slowing down or is it bogging as if its almost going to die
Do you mean the blinker bulb vs the brake bulb
nope you said you replaced the flasher, did you replace both or just one, if just one swap it with the other flasher in there. or see if your hazards work at all