1999 Chevrolet Suburban problem accelerating when hot

Truck has California emissions. It runs perfect in the cooler temps of morning and night, but in the heat of the day it has problems taking off from a stop or it will idle rough and stall out. Also if on the highway it will start slowing down no matter how far you are into the throttle and if you try to pass someone it woll downshift and act like it hits a rev limiter losing all forward motion. However, if you pull over and shut it off for a minute it will run a little better for a few miles and then start acting up again. It is throwing no codes and like I said runs great other times in the day. Please help.