So just an update on this. I have about 1000 miles on the swap and have got the ECU programming about where I want it, I think. I'm using a program from a '98 Passat AFN (B4), 028906021GL.
Amid break-in and a few dodgy tunes I've been getting about 30mpg 100% city driving. I still haven't convinced myself to cut the bumper for the front-mount intercooler, but once I do and I get some time we'll be able to take our first real highway trip up to see some snow.
I have also removed all body panels and sound-deadened and insulated at this point. I scored a giant sheet of neoprene from a random local guy and sound-proofed under the plywood as well. Throughout the whole van there are two areas of rust that I have now removed and welded in patches, and the whole thing is quieter now than it was as a gasser. We can actually hold a conversation inside. Since our (parked) TDI Beetle was demolished by a drunk driver, the bus has become our daily, so this is important.
Even with small (.205) nozzles, the van is drivable in city traffic and merging into rush-hour traffic in a way that would have been a major source of stress with the gas motor. Time will tell how it performs on mountain grades, but I am optimistic.