That P0443 EVAP code is becoming increasingly frequent lately. Much more common with the Rover 75 V8 than the ZT 260s for some reason. You can try checking and cleaning up all connections, or actually replacing the EVAP solenoid / Purge valve, but usually neither works unfortunately, I hear. If you do go that route, this or similar is the part (even in the US, original Ford Motorcraft/MGR ones are pretty much NLA).
https://www.amazon.co.uk/dp/B00BIDGM...B4aieDmuGx6c_I.
Alternative is to try buying that or a different make equivalent in the States, from RockAuto for example.
However you may well find that a new ECU or repair by (say) Chris Flanagan (Retro Sports Cars) is needed. Either way the ECU route will mean that you are looking at a bill of well over £200. A new ECU will need the correct MGR software, auto or manual and not Mustang, and then need installing with a T4 session on your car; your own ECU, repaired and recoded, would not.
You say "just bought"; did the seller not mention the EML code to you? He/she should have, I think.
What is the car's VIN (last 3 digits)? Maybe there is some history to be seen here on the Forum, but would only be available to view when you become a full member, I'm afraid. As well as lots of advice and information, you will have access to the Club Shop then too. Invaluable. That should be your priority I think, Dave. PM Tim, or send him an email at mg.zt260@ntlworld.com, and ask for a full membership questionnaire to be emailed to you.
David