I normally shoot split but played around with 3 under yesterday and all my shots were going left anyone know hot to fix this? I'm right on the money shooting split.

Not sure but sounds like the nock not only moves up but to the right when you hit anchor shooting 3 under causing the front of the arrow to point slightly to the left. Try shooting at longer distances and if they are more to the left then I believe that might be the reason. Just my two cents

It might be interesting for you to shoot both ways for a while without trying to fix the problem.  See which method gives you tighter groups.  If 3 under gives you tighter groups, then it should be fairly easy to make whatever changes you need to make to bring the POI on target.  But whatever change you make is going to feel unnatural for a while, so why go through that if you're shooting better split anyway?

Try to be more consistent on anchor and just trying something new.

Same thing happened to me when I switched from split to 3 under recently. To fix it I held my anchor a little tighter to my face to get the rear of the shaft more to the left and the point of impact to the right. It didn't take much adjustment of my anchor and that worked very well for me. It felt "funny" to me shooting 3 under for a few days but it was evident that my groups were tighter and I definitely am getting cleaner releases. I'm absolutely loving shooting 3 under now.