I've got a 92 rs 305. I'm changing out my air cleaner with a Summit open element one. I know one of these is the IAT-flat looking thing. Since I'm not using the heat riser function I guess I can plug off the vacuum port on the TBI unit where it goes. The second is a round one that has four little points on it-not sure what it is or it's function. I can't find anything about it in the Haynes manual. Can I cap this port off on the TBI unit also if it's not going to be used also?