JJohnston

So when i started my car yesterday, instead of going into its usual warm up cycle, the car did not hold a steady rpm, it was jumping back and forth from approx 1500-3000, once warm it idled at 750. Then half way to work it did not respond well to gas, if you got on the gas to much instead of revving up it would bog down, but if you just used a little gas it would act normal, and would go right through the rmp range??? Any idea what could be wrong? Today im replacing the fuel filter, which hasnt been done in a long time, and i think im going to put some injector cleaner in the gas. ps it a 90 n/a