2010 V12 Vantage 15k miles
I felt a very slight misfire which when scanned with my Foxwell NT530 scanner showed misfires predominately on cyl 9/10/12 generally in the 40 misfire counts range - there were no fault codes or MIL fault.
Tick over RPM oscillated between 730 - 780
I replaced all the coils (genuine AM - 3 pin), all sparkplugs NGK SITR7A11G replaced the PCV valves and checked the duck valves.
I cleaned the throttle bodies (about a teaspoon of oil in each manifold.
I flowed and cleaned all injectors - all checked out within 5%
There were no obvious problems with any of the components that were replaced.

On reassembly and after test run - no fault codes or MIL but misfire still there and if anything feels slightly worse.
On scanning - misfires on all cyl (except #4) between about 5 and 10 - cyl 9/10/12 still the worst - in the 50ish range
Tick over RPM still oscillated around 730 - 780
The Short term fuel trim is around +2 to +5 - Long term +6 to +7 on both banks
Fuel pressure around 385kPa (55psi) at tick over
Mass Air Flow around 3.5 g/s

Any suggestions?

 

Hi @UKRacer

Is there a CEL? Are you showing any codes, such as a P0309, P0310, P0312?

If you've verified both ignition AND fueling for misfire on these cylinders (reported misfires can be confusing and they are not limited to just ignition), then I'd start looking at the not so obvious possibilities - maybe the CPS? Are you getting any P0336 through P0339?

Best,
EDIT: - Sorry, looked at your post again, you're saying no MIL?

 

No fault codes whatsoever or MIL at any time before or after replacing parts
I realise misfires can be ignition or fueling or ....... but with the scanning information I have available I can see no obvious pointers as to the cause.