Hi,
Ive had 3 of these over the years.Like you I've just bought a k plater. If where you bought it steam cleaned the engine to make it look good, then it will run very lumpy for a while. The early 2.8 s you could steam clean every week without any problems but the 2.9 efi s were very wary of excessive moisture.You could replace the throttle control sensor( Shiny cylindrical metal thing top front of engine) or a couple of other similar items. Very expensive new from Ford these parts but well worth it in terms of better running.
Cheers and good luck. They are beautiful cars to drive day in day out. Ive got a 350bhp harvey gibbs prepared sapphire cossy but still prefer to drive the V6 on a daily basis.
NORMAN