For me, there were none, I think the farting is a plus.
I absolutely love this marker! With the J&J barrel kit, this thing shoots darts. I would reccomend using HPA with this marker or with any marker period. It's best that you get a barrel kit for this marker, because the o-ring on the barrel tends to break for most people, but not me. I actually prefer this over an open class phantom because of the balance and weight, the phantom feels odd and more like a toy while this thing just feels purely amazing.
Not to put the phantom down or anything, It's just my opinion. The milling looks good, it could be better but that is me personally. The double trigger is light compared to other markers like a JT-Tac5. You barely notice it when you're playing.
If you want to get rid of the farting, buy a spyder magnaport valve.
This gun is absolutely amazing! It's up there with the phantom.
A phantom costs 100 more, but if you put 100 worth of upgrades on this thing, it could possibly surpass the phantom. My setup in my opinion is better than any phantom.