When I ordered the update kit for my 44 Weber's CB asked me the application the carbs would were being used on. I told them they are on a 2.8L type 4 engine with a big cam 9.5:1 CR and 48/38 ported heads. They told me that is exactly what the update kit was created for. To give great air flow and still allow the drivability of 44 weber IDF carbs. Normally the engine would be best with 48 Weber IDf or IDA's if racing only but would be a dog for city and everyday driving. The updated carbs are drivable and also breath every as big as the carb body allows. The 38mm sleeve is paper thin and the removal of the secondary venturi really opens the carbs up. Major flow. A s I said they are running and driving great. I can see why they would not be for all engines. The kit comes with fairly big main jets (.165) which seem to be spot on for my engine. The plug electrodes are light brown in color. The kits had been out of stock for a long time and CB were telling people they had no idea of when they would have them available again. The week my motor was being finished the kits came back in stock. Good break for me. I would love to run tests with and without the carbs modified to see the actual gain in HP the kit gives. The pic below is just a little engine art. I took this pic today. It never gets old.