450es Not Running Right Since Snorkel.

Take some duct tape and block off 1/2 of your snorkel at the end. Then try. Most likely your lean.

You need to get a bigger jet. I would get a factory jet. On my 450, a stock
135 jet & puttin' the clip on the last notch down on the needle worked great.
I don't know what your elevation is, but that worked great for us. Hope this
helps.

Is it a homemade snorkle or the triangle atv snorkit kit? IF you are having low rpm issues it is most likely a needle clip setting and an air / fuel issue. You should not need to jet with a factory exhaust. Do you have the stock filter too? I suggest you put the needle clip on the last notch (closest to the point) with a washer under the clip, then turn the fuel mix screw all the way in until just snug, then back out 2.5 turns and see how it runs then. If its better but not perfect keep turning the mix screw out an 1/8 turn at a time until you reach a total of 3 full turns out on the mix screw. If you get to 3 turns out and it is still running like crap, then you will need to go get an OEM jet one size bigger than what is in there now. It takes lots of patientce and trial and error with jetting. However if you follow the steps I provided you, you should be pretty close to spot on, without the need to change the jet.