engine skip

Will do.

How do I enrichen the altitude compensating Bing carb at altitude?  It seems that it should actually be doing the opposite in its compensating role.  The only mixture adjustment I have ever done was the idle mixture screw as per the installation instructions from Vans, and my courses at Sebring (full in and back 1.5 turns).

1.  Low fuel pressure problem.  Higher pressure fuel pump  seems to have solved the fuel pressure issue!  Oshkosh and back with no problems.  Pressure with brief excursions into the yellow above the green, but never below the green.

2.  Skipping at altitude, improved with choke.  Even though I only had 70 hours and a year since the 200 hour carb maintenence by Lockwood, I sent them off again and replaced the jet needles and needle jets.  Skipping cured!  Best theory seems to blame fuel...last winters mix evidently was not good?  I use mostly premium auto fuel, occasionally 100LL and I am pretty strict about fuel age (at least since I bought it).   I keep the tank full, and use 100LL if it is going to sit over 3 weeks (I had surgery and it went three months idle in that time period).  It is always hangered and flies at least once per week.

Now back to the easy starting, smooth running engine it has always been.  So...how to prevent this from happening again?  100LL has some maintenence ramifications.  Different gas station?  I go to one that has a brisk business, national brand, but I'm not a chemist that can test gasoline.  I use a Rotax recommended additive  when I use 100LL.  Maybe just change the needles every 200 hours?

I would just try a different gas station.  If it was bad fuel, I'd guess it was less an issue of formulation and more one of contamination (particulates) if it messed up your jets.  What exactly did Lockwood find wrong with your old needles and jets?