what and where is the map sensor

doing a search i found a problem that sounds like one i am having with rough idle, and there fix was replacing a map sensor, thought i might try it to see if i can get her idleling right

Are we talking about your 1999 GMC 2500 or what? :uhoh:

That's MAF btw

Are we talking about your 1999 GMC 2500 or what? :uhoh:

That's MAF btw
my bad ,
my 90tc

follow the lil red hose line from ur fuel regulator and it will lead u to it, it should be on the back of ur intake manifold. but u also want to check all those vacumm lines..