Car stalls upon startup/rough running

[joshmeyer]

So I just picked up an 89 240sx coupe the other day....Here's when the problem starts. I go to start it up while its cold, all it does is bog right out. With someone hittin on the MAF with a ratchet while I turn it over, it starts. Has trouble idling while cold as well. Once warmed up, the car will idle and drive, but has a serious bogging issue around 2k, then sproraticly around 3k. I figured MAF was the issue, so I replaced it with one from a friend, but it's still doing the same thing. I've got about 3-4 more sitting in the room, so I'm gonna try continuisly replacing it, seeing if it gets better. Is there anything else that could be causing this?

NOTE- Theres a sensor inbetween the throttle body and the valve cover attached to the head that, when played with during idle, seems to cause the car to run better. What sensor is that, and would it cause this issue?