You might try to remove it HOT. The other solution is to soak it with a penetrant for a few days or if it is running, hit it with the penetrant when it is hot. I have used a product called KROIL. It is a industrial type penetrant. If you are going to CHANGE out the injector, after you put penetrant on it, TAP the sides of the injector with a ball-peen hammer. This sets up vibrations that helps the penetrant to seep in. One other way that I have used sometimes is to get a 6 point deep socket that fits the injector and use a half inch impact wrench. GET THE BIG GUNS OUT

__________________
My Truck.. 2007 DODGE, 5.9 Cummins, 6spd stick, 4X4. My car..1977 240D, OTHER WHEELS...1955 VW Oval window bug, European Delivery (Holland) with a 1700cc, 2 barrel, Porsche drum brakes. 1939 WILLYS Pick-up. 1967 Triumph 200cc Tiger Cub. 1976 Honda 550F 4cyl Motor Cycle.