90 degree design stolen from Buick
A few times in the past I have mentioned the problems with 90 degree V-6s particularly relating to tuning and vibration since a 90 degree V-6 does not fire evenly.
Buick had the same issue with the 231 V6 of the early 60s which later became the 3.8 as in Turbo Regals and the 3800 in Reattas. As I mentioned the only advantage to a 90 degree V-6 is that it can use the same tooling and assembly line as a V8.
In 1978 Buick solved that problem by offsetting the crank throws resulting in the "even-fire" V6 which could be tuned properly and resulted in some of the fastest cars in GM history, first with turbos and later with a supercharger in L67 form.
The was also the issue of Mercedes timing the dual spark plugs since there were only six coils.
Browsing through the FSM, I found this "The engine uses a split-pin crankshaft to provide even firing, and a balance shaft to compensate for the rocking motion which occurs with a 90-degree V-6." Sounds just like the engine in my Reattae.
Given even firing, the dual plugs (second firing 60 degrees after the first to scavenge any unburnt gas) now makes sense.
The exhaust system also looks remarkably like the one in my Pentastar Jeep. Only thing missing to bring it into this century is DOHC and VVT. And a 2.60 final drive. (Jeep has a 3.09 but also has 31" tires).