Hi. I just posted a reply but it did not work.

Try the WUR (Warm up regulator). They regulate fuel pressure during warm up cycle. Disconnect electric plug from cold start valve - not needed in our climate really.
Some K-Jet cars, I think VW, have an adjustable WUR and may well work with the XR. Have a google on them and see if it's failure matches your symptoms.
Maybe try a known working replacement first as fault finding?
Steve