4-Runner Starting Problem

I have a '95 4-Runner with the 6-cyl engine & Air Conditioning & 130,000 miles. Recently, it refused to start. I checked it over, pulled out the dirty air filter and it fired right up. Then I put in a fresh filter. Two days later it balked again, and started & ran OK after the filter was removed. Three days later it balked again. I checked for fuel flow, fed a bit of gas into the throttle body, found that it liked to fire, then found that it had fuel pressure upon cranking (after loosening a couple of the injector feed lines. Then checked the distributor & rotor. These were very worn, so I replaced them. It fired right up, ran fine for a day, then balked again. I removed the air filter and it started up, and ran with the filter back in place. I initially suspected fuel/air mixture preventing the start. What else should I check for?

A faulty MAF sensor?

The next time this happens check to see if spark is getting to the plugs. There may be an ignition problem causing this to happen.