So I have a 91 190Emercedes 2

So I have a 91 190Emercedes 2.3 8vall 5 speed. There is a noise that started out like a marble in a glass jar from around the alternator/water pump area on the front of the engine (I thought it was an alternator bearing going out). The noise is not there on cold start, only when it is up to temp. The noise has gotten deeper and louder and does not increase in speed with the rpms. It actually goes away when you open the throttle. (Or it use to). Now it is still rattling like a marble in a glass jar with a diesel type of noise from within the engine. When the car is turned off hot and restarted sometimes there is a loud metallic crunch noise as it turns over (engine mounts and tranny mount were replaced less then 2k miles ago). I have no idea what this noise could be and I can not seem to figure out if its the water pump, timing chain tensioner, timing chain its self, or some other problem. Car gets up and goes no problem, but I have had it stall out while idling at a stop light or even going around a corner at low speed (with the clutch depressed). And the idle will sometimes stick at 2kthe rpm but if I pull the gas pedal out it will down idle so I do not think that is related to the noise in question, please help!