yea you can use the u13 engine on the b14 but your whole engine management needs to get redone. your not going to be able to run the u13 ecu on it so whatever maf doesnt matter and you cant run a z32 on it without having a tuned ecu to match it with.
here are your options.
1.) ditch the u13 ecu and find a tuned b14 ecu like nistune, calum, nemu, jwt. then you can run what ever maf you want.
2.) make or buy a stepdown harness that will allow you to bolt the u13 ecu onto the b14 harness.
3.) get rid of the b14 and get a b13 se-r/nx and then find the appropriate u13 maf and use it all on that platform.