Use the idx.pdf file here
http://www.nicoclub.com/FSM/G20/1999_G20/1999_G20/ and go through the FSM.
You will need to make sure each of the 3 emissions solenoids behind the motor (black=egr, brown=map/boro, green=evap) are plugged in and the vacuum hoses are correctly routed to their corresponding system.
I recommend buying yourself about 4 feet of vacuum hose from an autoparts store, and cut off about 2 and a half feet. Unplug lines and blow through (the long vacuum tube you cut) on the back of the motor to understand how your lines are currently routed. Use the remaining pieces of hose to fill in cracked/missing lines. Look up each solenoid in the FSM to understand where each tube is supposed to be routed to.
Its a time consuming process, but really the only way to make sure things are correctly routed on your own (especially if you have missing lines or if someone was working on the car that shouldn't have been). The 99 g20's have the most complicated emissions systems of all of the sr20's.