I know that V8's tend to run a bit on the rich side and have black exhausts when running on petrol, but yours must be running on neat juice looking at those figures!!
Are you sure the air bypass hole in the MAF is free of ****e. The lambdas send the exhaust gas figures back to the ecu for the MAF to adjust to suit. Looking at your previous post about noisy tappets, I had that on my old V8 Disco and when I checked it, the camshaft lobes were almost worn into a circle, wonder I got any fuel into the cylinders at all...maybe another avenue to look at. Is the idle speed steady? For the price, may well pay to change the lambdas for starters, with what you are paying out in juice, it's a relatively cheap option. I also had a MAF go some years ago and the main problem was that the idle speed was erratic.