Engine running rough
 

So I am thinking it's a vacuum issue but can't find the leak. On hot days the truck runs rough at 1800 to about 2400 rpms and kinda smooths out at higher RPM but still iffy but from what I've seen on colder days it doesn't run rough even on cold starts. Also inconsistently bogs down during hard acceleration. No engine light is on and all sensors work including trans sensors so that isn't it. RPM in 3rd and 4th gear will stick at around 1900rpm at higher speeds and will not increase with gradual pedal pressing but if I floor it then it will pick up rev. If I hold constant speed where the RPM is sticking and slightly hold the brake pedal down alongside the throttle the rpm will pick up as normal and fluctuate as normal with gradual throttle changes. Need to figure this out before I drive to Boston next week. Help will be greatly appreciated.