I agree with the other forum members. It sure appears from the picture you posted that the pressure is leaking from the prechamber and/or burned/leaky heat shields. I would say that if the heat shields are old and someone didn't tighten the injectors to the proper torque, those heat shields will burn fast causing the problem you're addressing. The pre-chambers may be cracked, a lot more costly than merely replacing the heat shields, but I would think it adviseable that if you have injectors out and have the tool to remove the prechambers, pull all of them and closely inspect for cracks. There is a substance than can be applied to the pre-chambers that will show cracks not visible to the naked eye. I know another forum member posted on that substance in another thread, so you can do a search on it. If anyone ever used ether to start the car the pre-chambers really see some pressures they should never see. Best wishes.