The quality control of the last few Holley carbs I bought was pretty bad. Alot of debris found in the carb and metering block jet well area.
Now I take the carb out of the box, tear it apart, and clean everything.
While apart I check the bleeds and restrictor sizes with a pin gauge set.
If the metering bock don't have the screw in bleeds and restrictors and needs additional tuning, I put an aftermarket billet metering block in for tuning, then when the tuneup is good, I will duplicate the bleeds and restriction sized in the original metering block with pin drills.
I will dial in the idle mixture, throttle blade position, and transition circuit first.
If I want to really get the jetting dialed, I will use power valve block offs and a wideband O2 meter to tune the cruse / light throttle AFR around 14-15, then put in a high vacuum power valve, and check the AFR under load. Adjust the power valve restriction sizes to get a good rich setting around 12.5 to 13.0 under load.
Then put in the correct size power valve, and work on the transition circuits, accelerator pump discharge nozzle siza and cam profiles, and vacuum secondary rate if a vacuum secondary carb. If it has a choke, adjust the choke too.
FWIW, I have only had one carb that worked halfway decent out of the box at this altitude. It was an old Holly HP 1,000 cfm on the 451 stroker engine.