Update regarding the genny, we're running on backup battery system in the summer charging from grid. After inspecting the genset, I found that the muffler case is leaking from the folded edges, they aren't welded.
Flexible exhaust looks alright, the dirty insulation is caused by the air sucked behind the alternator where the leaking 2 mufflers exist.
The casing around it cracked for all sides (engine side) from vibration, and the 2 wheels on one side are bent outwards.
I deshelled the genset, and blocked 2 air outlets from the flywheel bell cover, maintenance is significantly easier.
Regarding noise, an additional mid-high frequency noise is noticeable from the flywheel fan (whine) , the engine is surprisingly less loud compared to the old 178f, more hum less clanking metal.
Replaced the muffler with AIO box.
I've been using a high temperature exhaust fan for ~2 years, its lukewarm to touch on full load as its sucking more cold air than the exhaust (~150W).
I've found that this is the only reliable solution for high hour operation with these jack hammers compared to flexibles (s-shape dry).
The wheels are also sunk and engraved in the concrete floor, the engine rubber mounts are still ok. The battery mounting platform is welded to the chassis, 2 of the 4 tabs broke, probably from vibration too.