I agree we you regarding ceramic size, nothing smaller than an 8 shroud, gives you better
Read the weld spec for your heat input.
Don't just take someones advice from off here.
Try changing your gas,
Is the gas lense the type with gauze on front or copper lense with holes in the sides.
If its the lense with holes in side change it for the gauze type.
Try putting a gas lense on end of your purge pipe, tends to give a more stable flow of gas.
Hope this helps.