The Fiesta ST is generally seen as a bit of a pain to use aftermarket management with, what with it having canbus...the stock ECU controls the alarm, immobiliser, air con, clocks and so on, not to mention as standard its a drive by wire throttle. Getting everything working perfectly with aftermarket management is not an easy job, its doable but really rather different from older cars where the ECU dealt with the engine and everything else was essentially separate! You have to keep the stock ECU and splice in the one to run the engine, not as simple a wiring job as on older Fords!

If you wanted to speak about what you'd need to fit aftermarket management to one AND keeping all the standard features I'd probably try and speak to someone helpful at Jamsport (who have done a few throttle body conversions with aftermarket management and managed to keep standard features like the clocks fully functional).