Dear people, I'm currently struggeling with a 308 GT4 and i hope anyone over here can help me with some of their knowledge. The car had a pretty bad backfire problem. First i went over the distributors (dual distributors with normal points setup), rebuild them, set them up on my distributor testbench so i'm sure they are working perfectly. New spark plugs, HT-leads. Coils and extensioners also checked on testbench and all is working fine. This made quite an improvement but it did not sort the backfire problem. Then i checked the obvious like fuel pressure etc. etc, noticed it was pulling false air at the base of the carburettors and the intake manifold so decided to remove and rebuild the carburettors/intake manifold. Took it all apart, ultrasonic cleaned them, replaced gaskets, needle valves, set float height, repaired the linkages, synchronized them and adjusted the mixture screws with a colortune spark plug. All fine and good, engine fires up at the first revolution, idles perfectly, no backfire at idle, all stable. It also drives quite good. Changed the idle jets (from size 45 to 50) to reduce the lean spot during progression phase and that improved as well. Strange enough with very little load on the highway it keeps backfiring. It must be somewhere in the progression phase because it is only with little load between 100 and 125km/h. It really feels like a lean backfire. Than i decided to put 55 idles in and slightly bigger main jets but the backfire did not went away. I read that i am not the only one here, but is there anyone out here that can point me into the right direction with my problem? One strange thing i noticed, when the car is idling all is fine. When i let it run around 2000RPM on idle, fuel starts dripping out of the acceleration pump nozzles. Than i thought, hey there is a 'check valve' inside the pump delivery valve (the screw that bolts down the pump nozzle) that might not seal. But it is not spring loaded so it is not supposed to seal if from fuel coming thru with low pressure but instead from air coming in..... Is there anyone that noticed this phenominom as well? anyway, long story but i hope there is someone out here that can point me into the right direction. It would be very much appreciated.