Dyno results - Tquad vs Holley vs Qjet - tuning issue, too rich

I also run a thermoquad i built per demonsizzlers instruction. I remember saying that the 1975-79 thermoquads will have 2 small holes in the front inside choke wall that need to be blocked off and the mixture screws will have to be changed to the 22 degree style if they are the 12 degree style. and also will need to add 4 more threads to the 22 degree mixture screws so they will work correctly. also said that there is a brass restrictor in the base plate that also has to be drilled out on the 850 TQ. I did what he said and still run this carb today, but can you explain why he had me do each of these things as i would like to learn why..I was 20 years younger at the time and didnt ask why and just did it, but now i would like to know the reasoning in plugging those holes and changing the mixture screw style and drilling out this brass restrictor..