vacuum lines?

[Maupins]

Vehicle: 96 S-10 Ext cab; 2WD; 67K; "W" engine.

Where or is there some way to find out where all of the vacuum lines are? I am pretty sure that I have a vacuum leak, I replaced the rubber tubes on the top of the engine(towards the rear) but it was only about 3-4 feet long, is that all that there is? and where is the rest located? how do you know what's a vacuum line and what's not?

The idle is all over the place, sometimes it's normal and other times it's sitting at 3k and won't come lower. when it's high RPMs like that if you shut it off it will diesel on. there is no pattern to when it will do it, it's truly random. And when the RPMs do get that high if you put it into gear it will get up to 25-30 MPH without me even touching the gas peddle.