I cant say for sure this is the o2 simulators fault, but I do believe it is.

Nearly anytime I drive soon after the car is warm, you can notice an ever so slight bucking of the engine. Its not harsh or anything; its slight; however its quite annoying. You have to have the gas steady, leveled out, and not moving your foot to notice it. Its a slight surge that lasts for about 1 sec on, 1 sec off (repeat X infinity)

This HAS to be the O2 simulator. The o2 sim is run by a 555 timer and my guess it that its giving the ecu either rich or lean feedback, resulting in the surging.

Has anybody had this problem or heard of it or anything?

ps- the reason I have the o2 sim in the first place is the car is a 98 dx and the second o2 sensor has nowhere to go as the car has no second cat any longer.

 

Well, if it's your secondary o2 that you are simulating, it won't adjust your fuel like the primary o2 will. The secondary sensor is just there to make sure the catalytic convertor is working properly. You could possibly have a problem with your primary o2 sensor. Or, it could be another sensor like your TPS, I had an ever so slight bucking problem with a car and it turned out there was a tiny dead spot in the TPS that could only be seen on an O-scope.

 

you could always check EGR flow