Not sure about the carb, you will have to measure it using some inside calipers
but the exhaust has a restrictor tube, I know this because I just bought one myself, I use a dremel speedclick arbor and the smallest cutting disc they supply for it...even then you may have to wear it down a bit in order to gain access
looks like the pint is mine then
This is the sort of thing you'll find, you can see the end of the tube in this pic although the 2A8 has a longer tube so you'll need a torch