1990 240sx basically stock...

Here's what the car is doing.... Start the car up, runs fine. back out of parking spot, drive out of complex, and onto the road. As I approach the stop sign, I put the clutch in, and the idle drops to just shy of stalling, if not all the way. If I stay stopped for more than a moment, the idle works its way up to 1200-1500 rpm. It drives fine otherwise. I can tell it is running on the rich side, it smokes a little. Accelerating and cruising, it is fine, but if you are moving with the clutch in, the idle is between stalling and 500 rpm. Once you stop, it works its way over 1200 rpm.
I thought it might be a vacuum leak, but I can't find one. The FSM suggests O2 sensor. I just put a new one on, still didn't help. I decided what the hell, and un plugged the TPS (both plugs) and the car doesn't run any different. Being a SOHC, I'm not too good with the motor specific stuff.
Is this a usual TPS issue, or is it just something else?
Is it that the TPS needs adjusted? if so, how?
What are the two plugs for on the TPS? I know on the DOHC, the TPS has two plugs if it was an automatic. This car was a factory 5speed. As far as I know, it is the stock motor.
Any other suggestions of what to look for?

thanks

 

FYI, by the time I even thought about the TPS, it was dark and I just wanted to get home, so I've not really had much time to check it out in detail. I've been looking for vacuum leaks and changing the o2 sensor all day...