I tried this combination just now and there is no 2nd curtain synch in P, Av, Tv, or M modes with the 540EZ in both ATTL and manual mode. I use the 540EZ with an EOS Elan/100 and an Elan 7e mostly and the 300TL with the T-90 but I've used the 540EZ on occasion with the T-90.