Thanks guys, great info, perhaps best to have the current items checked first and then decide to keep or replace. I had replaced the seals on the injectors a year or two ago, they seem quite durable.

This morning I sent JCL Injectors in Darlington an email requesting a price for a cleaning and testing as they do not have anything on their website. Darlington and Severna Park are both less than an hour away from me so that works.

__________________
2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.