That's right -- my mechanic also erred on the side of too rich, and it had to be adjusted a few clicks before the engine started running really well. It puffed out of the exhaust when hot and on part throttle. Best is probably to check it with an air/fuel meter while driving.

Backfiring when releasing the throttle can also occur because the throttle microswitch or the Bosch speed relay is not working -- or if you leave your foot on the throttle a little bit when deaccelerating so the microswitch doesn't activate.