I forgot to mention.
You do NOT have to change your carb. You may need to change or file your main jet on the dellorto. Do a plug chop after installing the pipe if it sounds like it is running decent(see wiki). It will tell you if you need to make adjustments. Typically you may need to go a number or two higher (example if you have a 52, you may need a 54) to richen the air/fuel mix. I just use jet files to enlarge the existing jet instead of buying bigger ones. Occasionally the pipe will fool you and you actually need a smaller jet. This is rare but it does happen. When I installed my techno bullet on my A3 tri-ped, it richened up (unburned fuel was going back into the combustion chamber) and needed a smaller jet.