Did it stick before replacing the grip? Was the throttle tube replaced also?
I installed grip heaters which I wound electrical tape over to keep in place and prevent damage before replacing the grips, one of these heaters was put between tube and grip (throttle side) and my throttle stuck..
I unwound the tape and the throttle became unstuck..
If there is too much pressure or squeezing on that tube your throttle will stick (being my point).
Also, if glue or something sticky was used to attach the grips and that slid into the throttle housing as you slid the grip back on.. may want to clean that out as that would be a prime suspect too.
Have you unhooked the cable entirely and pushed and pulled on the cable ends to see if the cable is slipping in and out of it's sleeve properly? If it's not binding at all, it's probably not the cable.