When using v1.1.2, the game lags when enabling shaders when using Iris. Switching back to v1.1.1 fixes it.

Can't reproduce it? I tried the complimentary shaders but the performance is same/similar. Also changes made shouldn't affect the performance at all.

Okay now it's not happening, I didn't change a thing. So weird.

Its something unrelated to this mod? Maybe you didn't wait for the world to load?