I'm new to the Datsun world and just purchased my first one being a 1973 Datsun 620 with a 1.6L. It was backfiring when I got it home and tracked it down to several disconnected vacuum lines which I hooked back up and/or plugged. This solved the problem. The stock air cleaner seems very restrictive so I am planning to replace the entire unit with an open air K&N style element. I've seen several pics that look like a square air cleaner and filter is used. Can someone point me in the direction where to purchase this? Also, since this vehicle is exempt from smog, I plan to remove the many vacuum lines. Other than the one to the vacuum advance on the distributor are there any other lines I should keep. Where should I attach the blow-by line? I think I saw a filter that is sold for this so I'm assuming I can install that to take care of this. Thanks for your help.