mk 1 gti not starting help

i have a 1.8 gti just put new fuel pump and relay on it but wont start if i take the top off the airfilter and open the flap it will start but as soon as i let it go it cuts out i have checked all pipes and there are none split and i have changed the air box still the same can any one help.........

paul c is the man!

i had this recently,turned out to be the coil,think the fuel pump or relay takes a feed off it ,i could be wrong..hope this helps...but paul c will tell you better,pm him

air leak maybe?

sounds liek an airleak, or the co/idle is set wrong. check the inlet boots for splits. also make sure the 5th injector is spraying fuel when car is cranking over on starter