As you say mart it would of been right when you put the chip and injectors ansd put the sniffer up the pipe . but over xmass we put a swedish plenum on it and it had a very bad back fire when on boost . so we put REX,s AFR up the pipe and re set it up but to be onist its been running like a pig and when its cold it back fires and so i new it was all over the shop . MART im going to send you a PM