I bought the Hush bolt for my Etek4 and it did make the gun more efficient, went from being sat around 280fps stock to 315fps with the Hush, but i had no end of trouble chopping paint, another one of the lads with an ego got the Kush bolt and had the exact same outcome.
Suggested to a mate with an etek to get the Cure4 and he loves it, been playing in minus conditions up here shooting different paints and hes not had a single breach or barrel break, the only choice has to be the cure4