Nissan Repair: 1986 200sx intermittend hesitation problem, spark plug wires, hesitation problem

Question
car spec's: 1986 (12/85) nissan 200sx, ca20e engine, 5spd. manual transmission, approx 100k miles.

the problem manifests itself by a hesitation,  almost stalling of the engine, it feels like the engine is not getting gas. This only occurs (but not all the time, the problem is intermittend and occurs maybe every 3rd or 4th time) after the engine is hot and has been shut off for a period of time (approx 10min to 60 min) and then is driven again. If the engine has been shut off more than 60 minutes and has cooled off enough the problem does not occur.
It is most noticable if I drive at a constant speed and hold the gas steady, then the hesitation  will actually slow the car down and the car will feel like I would cut gas off and on. If I put the car in neutral and just let the engine idle I have noticed that the idle speed will drop from approx. 800 rpm to less than 500 rpm.
The condition can be rectified by pressing the gas pedal all the way down and pumping the gas pedal about 4 to 5 times. then the hesitation goes away and the car will accelerate again and perform normally. This problem sometimes comes back shortly after the above procedure one more time but usually subsides.

I have replaced the PCV valve and checked all the vacuum hoses. I have checked the spark plug wires and the spark plugs have been replaced.
The fuelfilter and airfilter have been replaced.
the gas mileage has been around 25mpg for combined city/highway (50/50 ratio) which is better than the rated 24mpg.
I have added 'gumout' fuel injector cleaner to the last gas fill up and it seems to have fixed the problem for a while, but I am not sure if this is really a true effect .
this problem is more annoying than disabling and it has been the same for a while now (6 month) and it has not gotten worse as far as I can tell.

Any idea what I could do to troubleshoot and isolate the problem?

thanks in advance for your help and courtesy,

Rai  

Answer
I would be looking at the distributor to see if it is getting oil in it.  Under the rotor there is a cover that can be removed.  Also, you need to take the screw out of the post the rotor goes on and the two screws that hold the cover on and you will see that there is an optical pickup.  There is a seal in the bottom of the distributor that, when old, will allow oil to migrate up the shaft.  This gets on the optical pickup and then the car strats to cut out like you describe.  It is best to go to Nissan and buy a factory rebuilt so you will not ahve to do it again.  Also, the Nissan ones come with the correct cap and rotor pre-installed.