If you're experiencing a rattle on most cold startups then it is very likely that the oil pressure check valve is sticking open allowing the oil in the filter housing to drain back into the pan. On startup the engine has to "prime" itself and for the few seconds before before there is pressure the chain isn't held tight by the tensioner and it rattles. There is actually an updated part for the repair. It has a longer body to prevent it from cocking sideways and sticking open (which is how they fail).

I don't think the chain itself would cause the problem with the stretch you describe. I had one once where the pass. side ex. cam was 27 degrees late, without noise. Well other than it rubbing the valve cover.