Well, first off, newer Mitsubishi engines (since about the mid- to late 90s, really) have utilized hydraulic valve lifters (tappets). Used to be, valve "lash" (or, the sound produced by a gap between the valve ends and the rockers that sounded like intermittent ticking) had to be manually checked and adjusted.
Before hydraulic, you had to adjust this:
By doing this:
As the term "hydraulic" suggests, tappets in these modern engines require:
- A proper warm-up of the engine, and
- Good, clean oil
... to ensure longevity. We all know what a cold start run sounds like:
To get to the point, the only thing I would suggest here is to have the dealership check to see if there's any unusual tick at idle. The vehicle is covered under warranty for 10 years --- use it. Else if you really want to do this yourself, then know the tolerances for adjusting the clearance yourself.
Else, tappets do wear over time --- and that could either be caused by bad buildup or just improper maintenance. (e.g., cold start runs, bad oil, or dirty oil).
Now, last thing I'll say is this --- it's expected that, if an engine doesn't spin very quickly (i.e., low RPMs), that all the accessories in-line with the accessory and drive/timing belts will reciprocally not work very quickly. Of particular importance in this instance is the oil pump, which is also belt. When the transmission "drags" the engine because it's wanting to drive a "larger" gear, while the engine is working hard to spin faster --- THEN wouldn't it make sense for it to require more oil from its oil pump to keep all its internals lubricated?
That's why you have that tappet tick. Engine working hard, transmission wanting to drive on a larger gear. It's like you pedaling a bike from a low speed on a large gear.
I hope that makes sense.
Sad to say, no one in their right mind will want to (or even know how to) adjust the programming on the TCU to change this. So yeah. It's not that the engine isn't good enough --- it's the CVT and the TCU programming for the CVT that sucks.
Sorry for your troubles, and I hope this all made sense. :/