help have a little problem please!!!!!

[tics1982]

hi guys just got my fd on the road.when i start it from cold its starts straight away and drive it for an hour or so it runs fine but then turn it off and then start it again it will not rev properly just backfires.so was wondering if anyone could help me or have any ideas what it could be maybe a sensor like intake temp?

all help would be apprieciated

cheers luke