I changed out all of my pads to ceramic a while ago. When changing pads I did not re-install the shims. The were stuck so well to the old pads that I could not tell that they were shims until I looked at them very closely later. Anyhow, they have worked well and never made any noise, but since I changed them out it feels like the brakes may be dragging a little on the rotors while I am driving. It feels like I am riding the brakes slightly. Could this have anything to do with the missing shims? Do they serve any purpose other than noise management?

 

They also spread the force a bit more evenly and would prevent pitting/corrosion between the slave piston abd the pad. The other is the noise.

IMHO they would not change the braking, but are part of the system and affect the longevity of the setup. I would put them on the new pads.

The release of pads depends upon the run-out (side to side play) in the rotor and how quickly the fluid travels back up to the master cylinder. Till the pads move back expect some braking action.

Did you bleed or purge old fluid out of the line?
Any scratches/gouges on the slave cylinder wall?

Salim