Engine Revving Uncontrollably
 

My '94 MX-3 has been having issues ever since I bought it and they are getting worse. So, I have decided it is actually time to take care of them (hence joining the forum ;)). Most annoying out of all of them is this engine rev thing that it does. When coming to a stop, when I put in the clutch and brake (once the engine is warm), the tach revs from 1000-2000 RPMs. It does this until I let the clutch out slowly (foot on brake) to bring the RPMs down. I have been told a few different things, but most common is that it is a vacuum line. Does anyone have other insight into this, or know if it is a different problem? Or if it is in fact a vacuum line, how difficult is it to change?