A good place to start is with some data from a scan tool, you have one, yes?
I think you have to start from square one and go through a few things to make sure they are up to par. Scan tool data may focus your efforts right off. I'd start with
A Spring Cleaning. (GNTTYPE.org is down for a few days, when its back up this link will work.)
Tap the MAF gently with a screw driver and see if it makes a difference in the idle....If yes, get a new MAF. Replace the fuel filter, check fuel pressure, check for vacuum leaks, check for air leaking into the Turbo inlet tubing starting with the air box, Put a big dose of Chevron Fuel
System Cleaner through the tank, check the plugs, wires, coil and ignition....You'll probably find something to fix in that list.
Its normal for an LC2 engine to 'hunt' for the right RPM at idle (not 'miss'), that is, until you get a good modern chip in there. You need to confirm that the TPS and IAC are set exactly right too....
lee