1990 Toyota pickup 22re 4x4.
Has been doing this for years. But its sputters when ceuising at about 55 mph. If i push the gas down farther or let off it stops the sputtering. Go back to trying and cruise at 55 and it does it again (seems like there is a sweet spot in the pedal that causes it). Now it only does it in the summer months and never when it is cold outside. Maybe once a year it will throw a check engine light but it only pops up for a split second then goes off to not be seen for months. Any ideas? Maybe O2 sensore faulty or airflow issue?

try this video, dirty injectors often do that, or being THAT old, could be a starting to fail ignition control module. https://www.youtube.com/watch?v=bKGI9N_yWd0