I've driven a continental GT, a car built in somewhat the same spirit as the 850 (by that I mean a grand tourer, granted not much more in common) and despite its massive twin turbo (I think V12) the car didn't feel particularly fast. Now, without a doubt it was fast, but a 325is FEELS faster. As far as acceleration and a car being 20 lengths ahead, the last generation accord V6 6-speed manual sedan (yes they made it) did 0-60 in around 6.5, which is roughly as fast as a CSi, which had a significantly more powerful engine and a 6-speed manual transmission. Just like my 535iA gets beat easily by V6 sonata, an 850i would undoubtably get beaten by the 335i, a car known for having more power than BMW claims and beating E46 M3s when chipped. The last generation GMC Yukon Denali does 0-60 in 7 seconds.. the average car today is simply a lot faster than what was around 20 years ago. The 850iA is a great car to drive, and has power to keep overtake people on highways, but there are few races it would win compared to most new cars over 20k (maybe even less) sold in the states.
And, not to be annoying as I do respect the work you did on your touring and admire the skill with which completed it, but you're being very mysterious about what happened to the touring.. deciding not to do an engine swap certainly won't make it so you can never drive the car again. You have been alluding to something being wrong but, unless I've missed something, you haven't said what actually happen.. trying not to judge but its just a little sketchy..