JAGUAR E-Type V12 - V12 E-Type Carbs Part 2

Q
I was intrigued by the question from Daniel Chatillon (JWM March 2009), regarding the Burlen SU carburettor conversion for a V12 E-type, since I have exactly the same problem. Once fitted and according to the instructions, if I set up the mixture to be correct at idle, then I found it was lean above 2,500rpm.
Burlen, like you, advised me to check the fuel pressure, leading me to change to twin higher pressure Facet Red Top pumps (6.5-8.0 psi at 45 gal/hr), followed by an adjustable fuel regulator/filter. I also replaced the complete fuel return valve and painstakingly adjusted the spring tension to give as high a fuel pressure to the carbs as I could without causing float chamber overflow. This did not improve the lean mixture above idle, so I permanently installed a fuel pressure gauge in the dash so that I could monitor the fuel pressure whist driving, to ensure there was no fuel starvation at speed under load, which there was not. So I concluded that a lack of fuel pressure at all loads and engine speed was definitely not the problem.
To overcome the dangerous weak mixture above idle, I adjusted the carbs to give a good burn at 4,000rpm, and put up with the over richness below. I remained worried that this was not ideal so eventually decided on a complete engine rebuild by VSE as the only solution, despite the original engine having only covered 32,000 miles from new. However the beautifully rebuilt engine has exactly the same problem, and now I'm concerned that I will damage the new engine if I run it in with the incorrect mixture.
I am about to try modifying a set of needles by hand, but know that the correct needles must be available somewhere. If you could advise Daniel and myself on how to go about getting the correct needles, you will have two happy subscribers, and I feel many other users of the Burlen's SU kits.

A
The Burlen kit is designed for a standard car. With so many variables affecting the fuel/air mixture, including the air cleaner, exhaust layout, engine condition and even the altitude at which the car is driven, finding a needle that fuels correctly at all speeds and loads is a specialist job. In fact, once the external factors (fuel pressure etc) have been eliminated, it then becomes a job for a specialist with a rolling road and an accurate gas analyser. We would recommend consulting further with Burlen as it may be that there is a need for alternate needles in certain cases.