After engine warms RPMs stumble (question reworded) motor becomes jerky on long drives about an hour into trip. Can watch RPMs drop and jump about 200 rpm not all the time just occasionally but never when motor cold only when warmed

*CLASSIC SYMPTOMS* of a failing distributor!! .. Very common problem on the 3.3L engines .. I've fixed several of em! .. Suggest replacement of the CKPS at same time...

There's no doubt Nissan's have a lot of problems with their distributor's most shops will tell you that but there are many other items that can cause a bucking after hot. When it happens and losses 50 to a 100 rpm you would think of a miss or surge but at 200 rpm the engine is shutting down for a few seconds to be that dramatic. So, like pushrod is guiding you to a part that when it's electronic becomes oil soaked from the inner seal leaking in it, starts to breakdown. Normally we see them when on a short drive and the engine get to operating temp the stator or solid state module break's down and the engine becomes a no start. Your symptoms seem to be along the lines of long distance driving where several other systems would start to come to mind. You would think of the ignition system of coarse but also another problem with Nissan's we've seen are the TPS stating to fail causing the ECM to think you are letting of the gas pedal before it looks at other sensors like the MAF and decides there was a short in the TPS circuit. Most failures will cause a check engine light I would start there.