This script gets you access to Filter Sharpness hidden parameter inside VRayHDRI loader to get you sharper or blurrier texture ( LDR or HDR ). this way you can get even more sharpness in textures. but be aware of this can alter the speed of rendering a little by altering the sample rate.
the default value of script is the VRayHDRI default value. you can lower the value to get the blurrier texture or increase it to get the more sharper texture.

it is only compatible with V-Ray (tested with v-ray 3.5 and above but it may work on version 3 3,1 3.2, 3.3, 3.4 as well)

to use it just drag and drog the mse file or run it from scripting menu of 3dsMax