need a little rb25 help!

[ArBy25DeT]

here is my problem: when i start my car for the first time during the day it runs fine, no problems at all. air/fuel ratio is good runs and drives fine....probably after a good 30mins of driving the car, it wants to run lean at idle, like 16-17 a/f....and when im coming to a stop, sometimes it will cut off and i gotta crank it back on....now i talked to a friend and he says it sounds like the fuel pump...i have a walbro 255, maybe its gone bad? if anyone could chime in on this and help me out, would be much appreciated...oh and the car was tuned from a respectable tuner about 2 months ago and made 344whp and 300wtq....