I had change two of my O2 sensors and now I will try to replace the map sensor but can't find it. Do anyone have an idea of where it is?

what kind of motor, (what year is your car) if its on the LT1, its the sensor on the very top of the intake manifold,a rectangular black thing with a green wire harness clicked into it.

Did you get the car scanned so that you don't wind up replacing a bunch of parts for no reason??

1998 z28 and I did get it scanned and that was one of the problems. So went to the dealer and found out where it is, back of the intake values but now I don't know how to get it off. This is sooooo fustrateing....

Hey I did it, I will go back to Adance Auto and see what else is wrong. Oh how can I get more horse power but don't empty my pockets

you may want to get the car put on a scope, alot of times the scanners at regular auto parts store will think its something other than what it is.

example this guy i worked with kept going back to the auto parts store getting crap scanned and replacing it but still had the check engine light, finally the guy at advance told him it was his PCM that went bad. he went to the dealer and they said they would put it on their scope, turned out to be the Knock sensor was bad, and the pcm was fine.

From your description, you may be talking about the EGR valve. It can fail or just get crudded up and make the engine run crappy. It can be changed out but you need to get your hands back there first.