In desperate need of suggestions and help

[yellowcell]

Okay, heres the problem: Its a s13 1990 automatic, converted to a 1992 KA standard with SOHC pistons and new piston rings to bump it up on compression. I have been driving it for a good 5 months without problems. Now, for the past two weeks when i start the car it SOMETIMES idle high at around 1600 - 2000. and sometimes after a while it dies down to stock 800 -900. and sometimes it jut stays there. and when you drive it when it is idling high it bogs at times and when you get to a red light and down to a rolling start it dies down to around 900 but then rises or just doesent even go low, it just sticks at around 1600 - 1900. KEEP this in mind, at times the car runs fine! i put injector cleaner fluid, no progress. i changed the fuel filter, no progress. i changed the ignitor coil, no progress. Please help me out!!!!