Lumpy and ticking over at 500rpm?

Need a bit of advice, recently I fitted a 410 transferbox and now alsorts of things have gone wrong and some shouldn't really be related to the box, the speedo has stopped working, a eml light has popped up and now it's not ticking over well at all, really lumpy and sometimes dies when stopping for a roundabout or something,
Pic of dash


I did a full service on it a month ago along with a clutch so it can't need a service
I have taken off the pcv valve and cleaned it up,
Is there something else I need to check? Anyone had this before?
It's got 123000 in the clock
And it's on a y plate

Did you put a speedo converter on it

Do you mean the speedo pick up ring that comes with the ORA fitting kit?

Have you accidentally disconnected the lambda sensor when fitting your transfer box?

j999pre wrote: Have you accidentally disconnected the lambda sensor when fitting your transfer box?

thanks I will check that in the morning I think.