I'm running 509 8-71 blown motor do I need bungs in both risers or is one fine? Is there a side that it works better ? Going to leave them in there, going to mount gauge in dash should I go dual bank or is single what everybody's running? Thannks

You can get away with 1 bung, but keep in mind its only reading the one side.

I would recommend running two, one for each bank since your running a blower. Innovate Motorsports (I'm not affiliated) just came out with a single gauge, dual bank AFR gauge. This setup looks slick.