The RX7 my buddy bought was missing the air pump component of the emissions system so we assumed the previous owner did the delete. Is it necessary to put a dummy pulley in the air pump's place for proper engine operation?

 

Is there a dual belt system on the alternator? If so, the previous owner already took the proper precaution. If not, get a dual belt pulley for the alternator to reduce water pump belt slippage.

 

Now that you mention it there is! Thanks. That explains it.