What cause black soot to be in the tale pipe and it has lost power it a 2009 dodge nitro with 3500 miles

pull the trouble codes to narrow the possible cause.  It sounds like the fuel return line to the fuel tank may be clogged causing excessive fuel pressure to the injectors.  One or several injectors may be sticking open. one of several sensors may have failed causing the engine to run very rich.  You should be able to see black smoke from the tail pipe on acceleration.