Well, curiosity got the best of me, and I decided to take the carb apart and do a more thorough check of all the parts - against my better judgement seeing as how this carb is still under warranty. It's a damn good thing I did, Once I took off the metering blocks, I found metal shavings embedded in the metering block gasket where it mates to the main body, and some of those shavings came loose once the gasket was removed. The same thing happened to the secondary side as well. Come on, Barry Grant.
I know you can do better than this - better give the quality control guys a smack upside the head. What if one of those shavings found it's way into a main bearing? ...
... It looks to me like they came from where the entrances to the main passages to the boosters in the main body were reamed out to make the funnel shape, as there was still some small shavings still not quite detached from there.
I had some time today so I got a hold of an air compressor and an air nozzle with a fine rubber tip, and went to work blasting all the passages with 120 PSI of compressed air, to make sure none of the metal shavings made it into any of the orifices. Once I was sure the metering blocks and main body were free from debris, I decided to have a look at the idle circuits to see if I could find anything that might be causing me trouble. At first I did not see anything wrong, so I decided to blow air through the jets to see where the fuel was able to go. It turns out after some deductive reasoning and some time blowing air and blocking various orifices with my finger that I could not get any air to come out of the orifice leading to the transfer slot or idle discharge port (the part that is regulated with the idle screw). I tried blowing air backward through this orifice and it would not go anywhere. This led me to believe there was no way for the fuel to get to the transfer slot or idle discharge port. I didn't seem to have this problem with the secondary side. After some looking, I discovered a potential problem with the primary metering block, as shown in the pictures I have attached.
The secondary metering block has a hole drilled in the orifice shown in the red circle, while the primary metering block does not. My guess is that the hole is supposed to be where the fuel goes from the main well into the idle circuit, and if that is the case, the entire fuel supply of the primary idle circuit is cut off. This would certainly explain my dead lean problems. I would appreciate it if you would confirm if this is in fact what is causing the problem. If so, I'm going to need a replacement metering block under warranty, unless there is some way I can drill the holes myself (though I don't have much confidence in my ability to be that intricate with a drill). I would also need a precision drill bit set to have the proper size hole, and that could be costly. Please inform me on how I should proceed.