I've never had problems with my twin downdraft Webers except when I had a blowthrough SC setup. With the drawthrough they have been working great. I've been dumping huge amounts of fuel into the cylinders and my plugs still come up nice and clean. Stock Webers have 40's for both primary and secondary jets. I have two carbs and I run 210's in the primarys and 60's in the secondarys. I have gased my car up at the airport a few times with 104 octane with little or no results. No problems with the carbs. It just cost to much to run. I just stick with the 92 octane. Oh and the chokes, I yanked those out. They just restrict airflow.