The word "inert" means lacking the ability or willingness to move, act, or react. It refers to something that is not active or does not show any signs of life or movement. Full definition
I have been reading up on this, it seems that this extra throttle (if you really can call it that) is just there to increase suction and therefore flow of inert gasses from the EGR valve. (mechanics.stackexchange.com)
Case in point: his Work No. 202: Half the air in a given space, 1998, whose Robert Barry-esque ineffability (compare that artist's designation as works, in 1969, of quantities of inert gases released into the atmosphere) is belied by the infantine delight of seeing it embodied by thousands of party balloons. (highbeam.com)