2002 1.8L sentra bucks at freeway speed

[outThere]

has aprox 200k miles has the RE4F038 transmission. So when the sentra starts bucking, the tach stays steady, No fault codes from ECU. I use to turn off the OD for a few miles then back on again and that would take care of the issue for awhile. now it's bucking with the OD off. At a light with the A/C on or not after a minute or two, the idle will drop slightly and the sentra will start bucking and will eventually stall. at the light when the car starts bucking if i move the gear selector to Park or Neutral all will be ok.
by default the Sentra selects OD when I start the car. is OD supposed to be always ON? or just when the Sentra gets to a certain speed?

[VStar650CL]

Vacuum leaks from splits in the accordion tube connecting the airbox to the throttle body are super common on both QG18 and MR20 Sentras, and they cause a lot of weird, intermittent symptoms because the cracks in the pleats narrow or widen as the engine rocks in the mounts at different throttle settings. That's the first thing I'd check.

[outThere]

first, thanks for your reply. second I replaced the inlet duct last year, if it was the inlet duct, that is what you are talking about right?, if that had an air leak probably would get IAC, MAF, MAP ERROR CODES plus the car would have really bad acceleration/run lousy

[VStar650CL]

That's it, yah. For the most part they only throw codes when the splits get really bad, and then a lot of times they just throw an "I'm confused" code like P0101. Since it sounds like it's loading up at idle, what do the plugs look like? If they're sooty then you might have a fuel pressure problem or a leaky FPR.