Ive been snorting bupe for years n years n years. If you wanna do it the right way and feel your doses, space em out as much as possible. 2mg in the nose is actually a decent size dose (approx 4mg sub-L) but not too big. So let that first 2mg chill run its course, wait at least 6-7 hours then snort again, you will not only feel the next dose but it may even be a bit more pronounced. To snort 2 mg over a previous 2mg is not going to linearly affect you. Subs are not like other opiates. Less is more, that is for sure.