RE: Holy smokin' pipe Batman, lemme see that for a sec..
I have used that Harbor Freight aluminum solder to attach a thick pad of aluminum to where I wanted to tap the tuned pipe for a fitting. You could probably just go with a build up of the filler rod, then tap it. I've been told that the pressure tapping at the flange isn't the best place.
Recently I tapped a K&B.15 backplate hole for a #6 thread brass nipple and drilled a pin hole into the case. This works great, since this engine runs open exhaust.
If you are working with a system that has good pressure, you should be able to pull the fuel line off ahead of the needle [while the engine is running fast] and fuel will shoot out of the line like a little fire hose for a second.