TD4 white smoke and misfiring @ 2000 rpm

Well, my issue all came down to a bad MAF (Have a new one on now - only a cheapie but will get a better one in the next month or two) I have also replaced the intercooler hoses (well 3 of them £30 from fleabay) fuel pump and filter (also have done the R5 thermostat mod - wow) and changed to Esso Synergy Supreme+ diesel. Now have warm, quiet running relatively economical car. What a difference. I'm smokeless too! I can also recommend regular doses of Millers Oils (I went through 2 bottles in 3 months) to clean out the system and injectors.

I need to do the stat ,what do I actually need to buy and where does it go, I've had a quick look at some posts but I really don't know what I'm buying and what happens with the old one.

Was going to do this mod myself but found a post on here somewhere that didn't recommend it if you tow big trailers well I tow 1500 kgs with our caravan so I'm now undecided what to do apparently it causes overheating whilst towing

Oh not good ,that's why I got the Landry cause I have a caravan,Defoe put me off now