Get the diagnostic trouble codes read, then tell us what they are. Anything else is guesswork.
It might be worth taking it to a Ford dealer to get it checked on proper Ford diagnostics which can read all the codes. The generic readers the AA use dont always get everything.
I usually advise against using dealers as they are too expensive, but given how much money you have already wasted fitting new parts unnecessarily, lets try and fix it properly this time.
fred
November 2009