i have a 90 gt when the motor warms up (not over heating) it studdards or sounds like it is missing between 2,000 and 3,000 rpms the rpms will drop aboup 300 rpms it does it in every gear and also when i rev it up it i have had test ran on the motor and everything is fine does anyone have any suggestions

 

Could be a number of things. Timing, ignition, fuel etc.