rpms at idle speed up to 760 and hot exhaust lite

[mike]

Have a problem for a year now its happens every day fuel mileage drops rpms at idle goes from 700 to 760 rpms every day and hot exhaust light comes on ,take off at a light there is no pedal at first then it comes alive. fuel was running 8 to 9 mpg now 6.8 to 7.8 had a code come up 2 months ago had it cleared it was vg turbo controller the truck has not regen on its own, had to hook up to computer to regen it. ISX 15 , 870, 285,000 miles on the motor in a 2014 pete 587.