If the sealant looks sloppy around the cam chain covers its likely the chain has been changed, hopefully for the latest full upgrade kit including latest hydraulic tensioner. Very common on early CBZA/CBZC engines.
Watch out for loud prolonged machine gun rattles on cold starts, switch off immediately and then try a restart. Indicates the hydraulic tensioner has backed off and/or chain is stretched. High possibility of the chain jumping on the bottom sprocket or even coming off completely. Early revisions of the chain drive were both poor in design and of poor quality. So a revised design introduced over the course of 2012. More details elsewhere on this forum.
A slight rattle that only lasts a second or so is nothing too much to worry about. You get that even with the revised kit, but even then I'm inclined to switch off immediately and restart to allow the chain to align. Usually its nice and quiet on a restart.
In any case, avoid forcing the engine backwards, e.g. parking facing uphill in a forward gear. This pulls the return side of the chain into tension and stresses the tensioner which can slip back and even strip the internal ratchet and push it back and the chain goes slack.
So if you must park in gear then, if facing uphill, select reverse, or downhill, select first. Hope you understand the reasoning.
Another thing to check is whether the small PCV valve (about £16) has broken off. Situated in the back of the camvcover near the right, gearbox end, often found hanging on the rubber hose attached the airbox.
Again common on earlier engines and more detail available on this forum.
Check the ignition leads all read the same resistance (OE cables in 2011 are 9k ohm), reason being that cable to No.3 plug specifically often goes open circuit due to heat damage but the engine continues to work normally due to sparking internally, however this results in highly elevated voltages at the coil pack which then eventually breaks down.
New coil pack and leads are not that expensive (avoiding the dealer) Later engines are fitted with leads that have corrugated sheathing called "marten protection" which also conveniently protect the leads from excessive heat.
Otherwise, an excellent engine. (I shan't mention turbo actuators, I don't want to frighten you unnecessarily)