If the name of the game is weight.. and it does make a huge difference as you know WYO... I would ditch the injection and just pre-mix, the pump and the tank aren't much, but every pound counts for your project.
Things I did to mine-
BDX Kit- 5 lbs
Seat- 4 lbs
Tank- 5 lbs
Rear skid- 2 lbs
Headlight delete 10 lbs
Motor (Can)- 18 lbs
Oil delete 10 lbs
Never had it on the scale, but the tank and seat where the real deal. If I where to do it again I would probably try to go to something even lighter for a seat like what Burandt does. We never sit down anyway. I know that the rear skid is light, but I think there is weight to be saved there.
If I where building again without a budget-
-Stock cat front bumper
-Alt front end in TI- 6 lbs
-Jaws coated pipe with Diamond S TI can 18+
-TKI belt drive with oil delete 10
-BDX or whose ever's intake with headlight delete 12
-Trail Tank 4
-WRP Seat 4
-BDX drive shaft and flywheel kit 4
-Remove all idlers 5
-B&M boards Wash
that's roughly 60+ lbs right there for decent investment. For sure puts you quite a bit up on power and relatively the same weight. I would guess my old sled which had all those changes except the belt drive was somewhere around 410-420 dry and "felt" as light as the basically stock with a can pro's I ride with.
All the other things we already do, remove foam, etc.
You want to go SUPER crazy and expensive, go like Rob and those boys did and use carbon fiber everywhere, that gets into the 300+ per pound range however.
From all that you've GOT to be close to 400 lbs totally dry.