Car not running perfect.
 

!978sc with new top end. 964cams and old style headers no smog. Car runs fine at full throttle anything below 3 rpms and it bucks. Now it back fires thru air box when not running car hard. I'm new to 911s so maybe I don't know how to drive one correctly. It seems the harder I push it the better it runs. The back firing only happens when not running the car hard so when running it in normal traffic it will lose power and back fire thru the intake. Do I need to richen the fuel mixture. Or lean it out ? The air box has a pop off valve and is not broken.

I've heard that intake backfiring is a symptom of a lean mixture??? Mine does it occasionally when hot under the same conditions (not when cold though). Maybe try richening it a tad? Anyone else?