Definitely check the injectors. Test them out of the car if you can, even swap the 3rd and 4th cylinder injectors around with the 1st and 2nd cylinders to see if they will work in there.
I "cleaned" my own injectors once by using a fuel pump directly on the injector, and using an old plug and a battery to open/close the injector over a bucket. Not sure if it was right but hey, it worked...