P38A misfire

good morning all you wonderful persons
I have a a P38 range rover 4lt V8 petrol 2000 year model auto gear box
The righthand head gasket failed about 3 weeks ago so stripped it down and did both head gaskets. All of the faces looked good and flat after cleaning, put new valves all round in (before you ask I did grind them in and checked with engineers blue) after putting it all back together I have a misfire.
Put my trusty hawkeye on to find the code P0303 misfire detected catalyst damage - blocked or restricted injector.
My question is does this mean a new injector or are they reserviceable. I do understand in this through away day and age repair is very often at of the question but it does no harm to ask

Morning fellow 38'er, I'd swap the injector over to see if the issue follows first. The petrol units are usually a throw away item unless there is somewhere that does them?

They are not that hard to clean. You need a small battery to pulse the injector while having pressure applied to the a cleaning fluid can or reservoir. I did all mine on the bench last year: (unfortunately no pictures)

• Mount injector in bench vice with outlet into a small jar or other container.
• Fit an 18" tube onto injector & fill with cleaner.
• Then apply air pressure to the other end (I used 20 psi)
• Pulse the injector with 9-12V and you should see dirty followed by clean fluid coming out.
• Repeat until spray pattern is evenly spread.

A bit like this video, but I used just a straight tube connected to air regulator outlet & manually filed the tube from the can.