Idling Problem? Help

[boliztik]

Hey sorry if this is in the rong section i couldnt find the right place to post it but newayz

basically my sr20det runs completely fine but sometimes at while idleing usually at about 1000rpm it drops down to like 750? it never stalls or cuts out and usally i just tap the gas again bring it up and generally it stay there.

they guy said it was the something motor, dont think it was starter haha like top motor or something like that? has any 1 got any idea what it is? he said it was only like 65 but i wanna know whats it called so some mechanic doesnt just bullshit me.. cheers