loping idle on 86 4K

[jesse]

    I have been trying to settle the idle down on my 4K... but to no avail.
Redid the vaccuum lines, at least those that i could be sure of.  I know
that the O2 sensor is gone to crap and lord knows what other sensors.
    When i start the car from cold, it idles @ 800+/-, but when it warms up
a bit it starts to idle at 1200-1400. I can hear the RPM's rise a bit then
drop, over and over. Could this be the O2 sensor?  Or should i look
elsewhere?  The ISV seems nice and clean, and worked good before the engine
transplant.

Thanks, yet again,
Jesse Erickson