LOL
not enough to matter.
The peep must be tied in order to keep it from moving up and down the string

a peep with rubber tube will slow down string travel by as much as 5 FPS a peep without rubber tubing is about 1 FPS the serving will not make any measurabledifference at least shootingthru a chronograph.
if you were to sifer on TAP it would come up with some fractional number but not of any significance.