The world famous AMM (Air Mass Meter) is located between your Air Filter box and Thottle Body Assembly. It is held in place by a 10mm nut on my 86 model and a wired connector. Just Follow the big air hose from the drives side front and you can't miss it. When you remove it there should be a screen at each end of the part. Also held on by a hose clamp on either side. Easy to remove after you remove the connector that goes to the computer, the nut, and remove the hose clamps. Remove the hose from the bottom of the throttle body and check for pin holes, oil, ect... I held mine in my hand two weeks ago with great reverence learned from reading the BB. I was cleaning out hoses and checking for leaks and replacing the air filter.

I will leave the trouble shooting of it to the Guru's of the Brick BB. The best idea I have seen for troubleshooting is borrow one and see if it fixes your problem before you lay down all that coin on a maybe.