I also doubt the engine is running at peak EGT (best economy) at 130mph.
Modern car petrol engines run LOP all the time.
HP = Torque x RPM ÷ 5252
Is that not correct any longer?
I’ve done EFI re-programming and sold it in volume on modern motorcycles, and I would assume cars are similar. Above a certain power level, emission regulations and testing is no longer a factor and at that high power level Peter is correct that the mixture programmed into the factory standard fuel maps goes to max power, richer than stoichiometric.
Has Cessna actually delivered any Diesel powered 182s yet?
I believe they have. Using the SMA engine.
I think you’ll see a press release when Cessna delivers its first diesel powered aircraft to a customer. Searching around, I see no indications that its occurred. I can imagine that after engine failures on the C182 diesel prototype, one caused by something as basic as an SMA crankshaft machining error, the FAA and Cessna would not want to deliver a plane until 101% sure the bugs are worked out. The press release saying they’d restarted work on the Thielert powered C172 prototype indicates to me they wanted a backup. Does anybody have any data indicating they’ve delivered the first diesel Cessna?
PS Found this: FAA certification now stretched into 2015 AOPA Story November 4th
The one that I have in mind, and which incidentally crashed following an engine failure at takeoff, may have been a retrofit.
Sympathetic aircraft manufacturer helping Diesel gaining some ground in aviation:
Well, Cessna have delayed the deliveries of the diesel Skylane until 2015.
Aart, thanks much for posting the Robin interview link. Their comments on the economics of wood construction being good for low volume airframe production make a lot of sense, and I had never thought of it in those terms. 
