This horse just won't die. Sorry for bringing it up again, but this is about my fuel economy. I need more carb info and opinions on what's going wrong.

Here's the background.
I installed a pair of "rebuilt" 2-bolt SU HS6s on my 68 this weekend. I removed the 3-bolt units for inspection and cleaning and found one of the needles scuffed. I think I did that when I was last playing with the carbs and inadvertently lost jet-center. Hard to know how important that is until you have centered your own jets for the first time...

So, my new carbs are built of a pair of old grungy ones I picked up on eBay. These have a vacuum advance dizzy nipple, which is why I wanted to use them (I have a BL33 VA dizzy I want to try).

overall, the throttle shafts were barely worn, but there were no jets or needles and one dome was missing.

I bought a pair of NOS KN needles (which are B18B-proper according to my haynes SU Carb book.

I recently got another pair of grungy old SUs and took the dome and piston from them to finish my first set. I cleaned it all thoroughly, completely replaced the seals and installed the KN needles and pair of jets stolen from my 67 220 wagon. The "new" grungy carbs supplied a nice pair of needle-valves and one-piece plastic floats (no metal tab in there). I just cleaned and swapped the caps (AUD 2207, I think - same as my true "volvo" carbs)

So, my domes and pistons are matched to each-another, I have new needles, known good jets, new seals, tight throttle shafts, and *very* clean bodies. I put it all together over the weekend and installed it on sunday. Runs nicely, but seems to be starving for fuel. I got it adjusted to idle nicely when fully warm, but it'd choke a starve on the drive.

Pulling the choke would allow it to run just fine, but at best, that's bad for the economy. I had this experience with my HIF6s and it is one of the main reasons I gave up on them.

So, too lean right? I richened the mixture a few flats - same problem. Acts like not enough fuel, even though I adjust out 12 flats and slowly back them in until the idle changes. So... wrong needles? Doesn't look like it. I checked the 68's original carb needles and those are KN as well. (Note: The 67's jet used to be matched to a pair of SM needles).

Annoyingly the car would actually sputter and die while it was warming up w/o full choke. This happened at home and at work on Monday.


Questions.
So, I need to know a few things. Here's what I think I know - correct me if I am way off base.

1) Needles control the fuel mix relative to vacuum, right? the mixture gets richer as the needle is raised by the piston because the thinner part of the needle allows more fuel past? The needle profile is the most critical aspect of the system, controlling mixture through all ranges of the throttle vacuum.

The adjuster nut only raises or lowers the jet relative to the bridge of the carb. It just changes the "start" spot on the needle-jet relationship. The choke mechanism does the same thing by dramatically lowering the jet - super-richening the mixture.

2) there's only one style of jet for this period of carbs? Burlen lists the same two part numbers for the 1967 and 1967 HS6s. My 67 jets should work just as well as my 68 jets assuming no physical damage to the jet opening?

3) The Jet and Needle work together for the mixture, but the rest of the carb plays only a small role. (more complex I know, bear with me) So as long as I have the same size carbs (1-3/4") for a volvo, I should be able to slap any pair of good needles and jets in it and expect it to work - aside from air leaks stuck pistons and whatnot?

4) I see DX needles mentioned for these cars. Is the KN really correct? Could it be the source of my lousy economy and inability to get them properly adjusted. Are KN's too rich? Haynes says they are "standard." The 68's old (3-bolt) carbs idled and revved smooth, but always drank too much...

5) if it were a float/needle problem causing lean...ness, then it should utterly starve under high idle (high consumption) not at low idle and the choke should kill it even faster, right? I'm ruling out the float/needle combo for this reason.

That's it for now.

After 60-70 degree temps on the weekend, we got hit by a huge sleet and snow storm, so I can't mess with the car for a bit. I figure now's the time to get straight on some things.

Also keep in mind I've got at least 5 similar guides and two books on how to properly adjust these carbs, I need trouble-shooting help - not as much with the basic procedure... but any help and info in appreciated.

Thanks as always.