WE G17 and WE mp5

[AirsoftYeti]

im having issues with both my WE gas guns,

G17: will only fire a few shots with a full mag of WE green gas and very quickly loose power and stop cycling, i remove the mag and manually press the valve to fine plenty gas left, only non WE parts is the maple leaf hop/barrel drop in kit.

WE mp5: i had to replace the nozzle as it was damaged, so while i was in the gun i replaced the nozzle then the inner barrel and hop rubber with parts that was recommended to me from the mp5 owners group on facebook, since then it dose not seem to add any lift to the BBs. This also happens when i refit the original hop and barrel, gun was shoots 340 fps and i was trying to use 0.25g BBs.

cheeres for the help in advance