casting help needed

I am an experienced caster with 25 years experience. Lately I upraded my old
8 foot #3 trout rod with a faster actioned modern #4. I found that I changed
my casting technique with this rod to use the wrist slightly in a controlled
manner to work the rod more for its extra distance. I got bad wind-knot
problems and tangled leaders with the really tight loops. I was getting
great distance and speed with the flyline itself, but the leader was getting
really messed up in comparison with the wider loops from the old slow #3.

Is my technique wrong, or is my flyline too light for the rod? I am
suspecting that the line (SA Aircell 2 Ivory #4 DT) is too light for the rod
(Missionary 8'3" #4), and hence I feel like I need to work the rod with
slight wrist flex. Wrist flex can put waves in the flyline and mess things
up at the leader end, so maybe I need a heavier line? I never casted a fast
rod like this before so don't know what the effect of the blank might be.

Anyhow, my general point is that when I am casting very fast tight loops
with this rod / line / leader, I am often getting tangles. Is this usual
with fast fly rods? If so, how can it be corrected?