A friend of mine had a similiar problem on his 2k Maxima SE. when he disengaged the clutch, the idle would undershoot to 200-300 RPM's, sometimes it would die, sometimes not. It would usually find itself around 500 RPM, the idle when he bought it was at 750 RPM. A simple computer reprogramming solved his problem.
Have you put the OEM MAF back on to see if it restores your idle? If you do and the idle problem continues, then get to the dealer and have him fix it. If the idle problem ges away with the OEM MAF, . . well don't know if I can offer anything.
Good Lcuk,
david
