Did you mean to say no muffler at all[X(] or just not a modified muffler yet? The right back pressure (at the right time) is a big part 2 stroke tuning. With no back pressure the intake charge can blow right out the exhaust port at certain RPM. Trouble is with bigger carb the stock muffler can have too much back pressure esp. at higher revs. A good set up witih 11mm carb is replace the 1/3"ID exhaust outlet pipe with 7/16"ID. Bigger than that is not necessarily better. Means a little cutting and brazing but at any rate I wouldn't try to tune the intake without the muff you intend to run.