Fresh SR swap, Weirdest Idle Issue! idles UP!

[Glocky]

Ill be a little specific, cause this is a dumb story.

I bought this car 8 months ago and it is my 4th 240sx. It came with an RPS13 SR in it. Long story short that motor died. I got a REALLY good deal on another SR Redtop and installed it. Everything went smooth until we cranked it up. First off, it is loud as anything. sounds like a lawn mower in your face. and also the really cool part, it starts at 2,100RPMS and climbs its way smoothly to 5,000RPMS. and then very slowly climbs 100RPMS at a time till i shut the motor off. i have been all over this engine. and this is my 3rd SR swap. NOW! another odd detail! I found a random wire that goes from my ignition area (under steering wheel) and goes into the engine bay. I DID NOT PERFORM THE ORIGINAL SWAP! so i have no idea were this came from! Now here is the main of my question. Were the O2 sensor clip meets the harness, there is a lone black wire with solder on it. so i have 2 disconnected wires just laying in my engine bay. there are 3 wires going into the clip for the O2 sensor and 3 wires coming out of it to the turbo.

(there is a single string of 4 wires, 3 go to the O2 sensor and 1 just sits there. Should this wire (that goes back to the ECU) and the one from the ignition be wired together?)

-------------------------------------|____________|-------------------------------/______\
-------------------------------------|O2 Sensor Clip|------------------------------|Turbo__|________Not Connected-----------Ignition Wire
-------------------------------------|____________|-------------------------------\______/
--------------Random Wire that goes from ECU and is taped to these 3 O2 wires! <------------------------^Do I connect these? Will it hurt it?

[OutToWinPAHC]

I'd say check that wiring, but it sounds like a coolant temp sensor to me.

[Glocky]

I think it might be the IACV. i have most of the black top parts so ill swap the intake manifolds.