My '99 nissan maxima idles rough at a stop, comes n goes, seems worse while in "Drive"..... When i let off gas going down road, instead of tapering off, it seems to "drop" roughly....also going up hills when it seems to need fuel most it seems like its not getting enough and hesitates....it finally threw a code for knock sensor, replaced it, light went off, i have also replaced fuel filter, air filter, plugs (the NGK iridium) cleaned MAP sensor with appropriate cleaner. She runs good on highway.....im lost.

 

Probably a failing coil causing a weak spark.
Pull the coils plugs one at a time and see if you can find the cylinder that's acting up.