Engine KA cutting out

[95se]

Couple of wks ago I was driving along and all of the sudden there was like no power. Then it felt like whole engine was stopping then start going again. I had an injector go bad once but this was worse. Could hardly drive it. I took it in to mechanic just after the check engine light came on after a day after this started. Mass airflow sensor and knock sensor codes were thrown. Taken him two weeks to check and he's still not totally done. Says both sensors are ok and the wiring to knock sensor is fine. He suspects the problem is somewhere in the harness going to the maf because the voltage was low at the connector that goes into the maf but the connector itself looked good so again he things there is a short somewhere in the harness. He said he could run a test wire from computer to the maf somehow to see if the voltage is good. If it is then the harness is bad if not then maybe the computer is not good. He says from his experience that there are problems with harnesses and connectors on most Nissan vehicles. So if I do need a new harness where is the best place to get one and should it be the harness that goes all away from computer to the maf? I am really not knowledgeable on wiring so thats why I'm asking. Thanks for any useful info.