Marshall: Carb adjustment (flow) tools: I've found that the flat saucer version with the tube sticking up doesn't work well with our carbs. Instead, get what we all call a "snail", like this:
https://www.cbperformance.com/product-p/6537.htm
You remove the air cleaner and stick the rubber snout down into one carb throat at a time to measure the flow on each, then make adjustments to even them all out. You'll have to measure the throat size in your carbs in order to select the proper one.
There is a tutorial on this site somewhere which walks you through the sync process.