Engine Seems Weak. Some sputtering?

Alright, I have a Honda Civic EX. I changed the oil, spark plugs, and cleaned the fuel injectors. The car runs fine but when I slow down to a stop, the car engine shakes violently and the RPM goes really low. There is a little sputtering as well. Could this possibly be my engine itself (ex: pistons or cylinders failing?). Much help appreciated.