volvopentaman

Not the fuel pumps, if only one bank lean, 100% sure. Fuel Pressure regulator probably not faulty, because it would throw a code for both banks, as both banks share both same FPR and pump(s) and filter, cause there's only one fuel line to the engine from the tank (+ the return line).

I'd put my money on either an intake leak, a really small one is already enough, just a missing vacuum hose did misfires on my W12, because the ECU is programmed so exactly to burn as little fuel as possible.

Other options are faulty/clogged injectors, injector O-rings (these were rotten on my W12) and electrical problems with the injector + side. - feed is from the ECU, so i would not suspect that, but it's also possible.