Ok before Anything else:
-end of last year the car had 80000k engine installed
-January had a pulley, the belt, aircon compressor replaced
-Was serviced 3 weeks ago
-Hit a piece of metal on road while driving last week and put a small hole on bottom of manifold (which I temporarily fixed with muffler putty)
Now today I noticed it making this inconsistent rattling noise which seems to be coming from left hand side of engine.
Any ideas as to what it could be? before I take it to mechanic.