2001 Spider Lose of power AFTER tune-up

Hello, Great webs site. I have a 2001 Eclipes spider with a V6 with 130,000 miles on it. I desided to do a tune on it. I changed the spark plugs and wires, after completing this task I started the car. When I put the car in reverse it bogs down and almost dies. I looked at all of the vac hoses, and wires trying to find something not hooked up or lose, I found nothing. I then changed the cap and rotor, with no change in the way the car runs. Now the car is giving me three codes of P0300, P0130, and P0300. These told me that there is mutuble miss fires, and that the 02 sensers are bad. I got two new O2 sensers installed them with no help to the performace of the car. Giving up I took the car to a auto shop to have a diagnostic done on it, they came up with bad fuel injectors. I changed the injectors with the same outcome with the car. As of right now I have new injectors, plugs, wires, cap, rotar, O2 sensors, and a new upper intake manifold gasket. The car was running fine when I started the tune up now it is one sick puppy. The exaust coming from the tail pipe is smelling like the car is running rich, but with no smoke. I know that there are lots of things that could still be wrong with the car, but I do not have the money to keep throwing parts at it or to have a mechanic work on it. Could one of you help me with what could still be wrong with the car or what I should check next? Thanks in advance!