1999 Mazda Miata Idle problems

Ok here is the problem with my 1999 Mazda Miata. It began running rough. By this I mean upon start up it would idle irregularly. RPM would lower and fluctuate between 12,000 and 0. Upon warming up it would idle at 850 rpm�s and then begin to drop rebound drop etc. Runs better but not perfect when warm but sometimes it will stall out. When warm on the road if I was going from a dead stop I would have to rev it up as I was fearful it would stall out as I pulled into the roadway. I also noticed a hesitation upon stepping hard on the throttle (even when not under load such as with the clutch pushed in). Once running at highway speed it seems fine however it seem like I do have a lack of power but I am not positive of this.

Here is what I have done. I replaced the spark plug wires and checked out the plugs, which were in very good condition. I put a new air filter in. I cleaned the throttle and cleaned the MAF sensor and even switched it out with a friends working MAF Sensor. Did not change anything. I adjusted the linkage on the throttle which did help but not eliminate the hesitation.

Other things to note. This car is only driven from May through October. New gas filter, plugs 10,000 miles ago.