It is a RZY2955 on my boards (China made) note the number 2955 can also refer to a bipolar transistor, but this one is fine.
When you said 340A I became a little bit uneasy...
The only thing I find is an IRF340 ... This however is a N-channel MOSFET, whereas the 2955 is a P-channel MOSFET...
Can you find out what is really on your board? Where did you get them from in the first place...