Altima 99: Engine idles unevenly and vibrates.

My engine revolution is uneven, fluctuates between 900-1000rpm when starting from a cold temperature. when its temperature is higher, maybe after driving around for sometimes, it starts and stalls. also, when on idle, it vibrates. OBD-2 scanner returned MAP sensor and Throttle position sensor problem. I ve replaced the throttle position sensor but it still does that. I did not replace the MAP because I dont its location and becos I read that most times, the MAP malfunctions because the throttle is bad.
I will appreciate any help on the MAP location and any other help to solve this. thanks