I have a escort mk4 1989 with mfi and it wont idle at all, it runs great when revving past 2000rpm but as soon as I let go of the gas it dies. Engine has been rebuilt, bored to 1.74l from a 1.6l. Head has been dropped about 2mm and it has a 279 cam. The engine is high compression. All other parts have been replaced or cleaned and new seals. What would cause it to not idle?