2.5 POOR RUNNING on TFS54

[TopCat1968]

Hi- ive just joined ! wonder if anyone can help here

i have a 2002 TFS54 with 2.5 TD
it suffers very poor torque and get up and go from the off for a while now

even went into limp mode after i lent it to son who embarked on a long trip- Inverness- Tidworth. engine light briefly came on.
urg!
i see somewhere here there is an issue with cardboard filter on EGR valve?
it had a full service in nov and hasnt been used since(although im not sure he had both fuel filters available then); i took it it to someone in inverness who confirmed it wasnt the MAF - HE DIDN'T HAVE a computer that could read the codes.

i contacted tuneit for a souped up ECU but they couldn't fit it- so refunded me

when possible i aim to fit new filters, check the computer for the fault code with dealer with th correct kit. son has to get back from abroad first (feel guilty about lending him a problematic car after he crashed his old one)
its only done 83k and is in VG order- having spent zero time in highlands salt over winter
all suggestions about where to go from here gratefully received
HELP?