Noise coming from timing chain!

Any abnormal noise coming from the engine needs to be investigated dealt with before it causes you extra problems and expense. If you have a worn and sloppy timing chain it will effect your valve timing and ignition timing and can possibly skip a tooth and then run really roughly so that could be your problem. But you say you have two cylinders not firing right, with the timing chain they would all be bad so it could be something else. With the engine idling take off one plug lead at a time and note the change in engine sound. If no change this is a the bad cylinder. If the two bad cylinders are adjacent you may have a blown head gasket (look for a milky residue in the oil, foaming in the radiator and overheating). Once you have tried this report back with your results and you can get more help.