Allow me to disagree to that statement.
The LC engine was launched with the 2013 models, and compared to the competitors, it is the newest engine. (I might be wrong, but as I understand it, Ducati, Ktm, and Thriuph newest engines are based on modified older engines).
True, the engine would benefit from a richer mixture, but BMW as well as any other manufacturer are restricted by legislation. They keep improving within the boundery set upon them and I understand that the latest versions of software the engine performs fairly well.
Even so, a bit of richer mixture would still make a sweeter running engine, and that's where 3-part mods enters the arena.
Hilltop is one of them, AF-XIED is another option.
Most of the claims regarding the improvements are actually made by the owner of the bikes. Hilltop them selves are fairly moderate in their description.
And frankly, as long as the only modification you do to an engine is adding fuel, the result will at best be modest when it comes to gain in power. However, the way the engine behaves may be felt as lots more. The lean running makes the engine vibrate slightly, and it chokes easier at low rpms. To many riders this improvement alone may be worth it.
It is my humble opinion that Hilltop and AF-XIED does pretty much the same to the engine for all practical purpose. The cost are fairly the same, the difference being that the HT-job does it internally and AF-XIED is an external ad on.
So, now that I make such a bold claim as comparing the HT to another product, am I suicidal? Allow me to explain before hell brakes loose.
HT claims that the engine is still able to adapt to different cans and set-ups. This means that O2 sensor is still in use. And as long as the O2 is considered, the modification to engine managment must modify the suggested correction from O2 in order to add more fuel, as is the case with AF-XIED.
In order to make a dramatic change to the behaviour the airflow through the engine needs to be changed, and both options above only affects the fuel. Sure, ignition may be affected as richer fuel burns faster and thus a slightly change of timing as the mixture changes may do well. But we are taking small changes here. Remember the HT job is clamed to improve the gas-milage, and that excludes heavy changes.
What about the Dyno-charts before-after?
Well, some of the guys have been kind enough to share they Dyno-charts. The thing is though, all the after-charts that I've seen shows pretty much what you may read from dynocharts made by others (plenty of them on the net), while the before-charts shows ridiculously low output. Again, I will remind you of the claim from HT that the gain in power will at best be modest, it's all about how the engine behaves better from getting slightly more fuel. I can not explain the low before-output, as it does not make sense.
That's my saying
Shoot!