One of the signs of a blown injector gasket is oil in the fuel. You can tell when this happens because your fuel filter gets really black. Another sign is if your engine is using oil and you can't find any leaks. Thats because your oil is going in the fuel tank. These are the orings for the injectors.
Don't forget if you pull an injector get ALL of the liquid out of the cylinder before you replace the injector. You will do serious damage to your engine if you don't.