Hello everyone. This is concerning a 1987 TII. I recently installed CorkSport's full exhaust system and I had to remove a small pipe that ran from the engine to the stock exhaust. I was wondering what it is, and do i need to cover that hole with a plate?

 

Sounds like you are referring to the split air pipe. It is used to provide air to the main catalytic converter under cruise. Since you have essentially disabled the emissions system, you can remove and block off the ACV and remove the air pump. You will need to get a dual belt alternator pulley to compensate for the missing air pump drive belt on the water pump.