im not really familiar with nissans. the only nissan MAF ive ever seen was tiki's and the one i had on my s13 that i pulled the motor out of, but a quick MAF fix is to take some Brakleen and spray it on the sensor wires in the middle. then take some electrical contact cleaner (~$10 from radio shack) and spray it on both the MAF side and wiring harness side of the connection. how do you know it stops reading after 2500rpms? id think a service engine light would pop on if the MAF was not working. does it only cut on after 2500RPMs? fill us in on how you came to that conclusion. good luck

and you seriously need some help or a hookup at a dealership if youre paying $800 for a MAF sensor