I have a 93 jeep cherokee 4 liter, 6 cylinder. The problem is when I fill the tank past 3/4 full or let it dip below 1/4 and the weather is above 70 degrees it wants to stall out on me upon acceleration. Ive taken it to numerous mechanics who test the pump and lines and can find no problems. Does any one know anything regarding this or another viable option to try??

Have you changed the fuel filter?

Remove the air intake and examine the throttle body. It may need cleaning. Replace the air filter, if it hasn't been recently changed.

Most performance issue are electrical-related, not fuel. Have you gone over your electrical system and recently replace spark plugs, spark plug wires, distributor cap, and rotor? Have you tested/replaced the Ignition Control Module and coil? Check for any vacuum leaks, particularly hoses going to the MAP Sensor.