Are you using a Metallica needle? This is a necessity with specialty threads, which wear down quickly with the friction of going thro the needle eye. The Metallica is specially designed for the more fragile and beautiful threads available today, and use the largest size, 90. Also, when fmq, I use a fine thread made for bobbins....available anywhere. It's thinner and somehow makes the stitching more even.
Hope this helps.