I finally have mine running; thanks to everyone who has contributed to this. I didn't do anything since my last post, but the next day everything worked.
I have a FrostHeater in my Jetta wagon. I don't see any way that it would work in this car.
A couple small tips that I would add for this job:
1.) The CAN bus wires are ridculously hard to get at near the main connector suggested by Kufatec. Were I to do this again, I would find the CAN bus elsewhere. The particular bus that this has been assigned to has changed over the years based on old-VW CAN bus Service Tutorials and new ones. SSP-470 is a more current version that seems to best reflect my car. I noted that the TPMS, trailer controller, and front seat adjusters all tie into the same bus (OR-VI is CAN high, and OR-BR is always CAN low, regardless of the bus). Track down the wires elsewhere and tap in there; under the driver's seat is where I would be looking.
2.) The extension connector for the circulating pump on the Kufatec harness is the correct one for the magnetic valve. If you do not have access to a replacement connector and crimp connectors, cut that connector off with a pig-tail and splice it into the magnetic valve connector. Then simply solder and heat shrink the existing factory harness to the Kufatec extension for the circulating valve.
3.) You can tap into either the left or the right fuel tank if you are using an aftermarket pick-up tube. The left tank is larger and should work better. When you remove the seats to access the fuel sender, you have to remove the bottom seat cushion on the side you are working on. You can sometimes get those out without breaking the clips that hold the cushion in, but it is hit-or-miss. The clips are meant to be destroyed in the removal process; they are part number 7PO-886-373A and are referred to as "grommets" in the parts diagram. Also on the subject of seats, the triple-square bolts that hold the back of the seat brackets down were extremely difficult to remove, mine rounded out 1/2-way through the extraction process. I ended up having to weld my beloved Snap-On triple-square to the bolt to get it out. I can get part numbers for those bolts if others have this trouble; it appeared to be some sort of super-high strength thread locker.
4.) If your heater does not come with all the brackets, there are hexagonal holes punched in the bodywork for installation of those brackets. You are on your own in terms of making the brackets, but the hex holes in the bodywork are about 9.5mm across. I found that you can pound in a 10mm (wrench size) shouldered nut into these holes and they will not come out. Welding is another option, but I did not think it was necessary.
