Idle problem
 

I have a 1987 Saab 900 turbo, and recently changed my injectors but am having major problems idling. For the first minute or so, I'm idling at an even 500 (which I know is way too low) but then it starts getting irratic aand spiking to around 2500 or 3000 or at some point 4000. I did all the adjustments I could and I can't figure out why this is still happening. Any suggestion?