2006 Chevy Colorado Misfire

Recently I had my colorado in for service on the check engine light. It had been on for a while and I had been having issues with the car hesitating, and even stalling out at idle. I was told that the O2 sensor was bad and needed to be replaced and that the reason was that there was a lot of carbon build up on the injectors that needed to be cleaned. I was skepticle b/c my car was in for a warranty item and that the injector cleaning was not covered and you know the reputation a dealership has with uping repair costs. I had the o2 sensor replaced and when I left the lot the engine light came back on ( I am assuming b/c of the misfire I was informed about). What are the best ways to go about this issue? Do the cleaners like techron, or lucas oil fuel treatment work?