I'm having the same problem, put the car on the dyno and she is perfect at a 11.5 AFR until she hits 4500 rpm or so and then starts to go lean. The good news is that she pulled 393 rwhp and 457 rwtq, but was in the mid 12 afr and climbing. We adjusted the Leask but it didn't change, going to check the fuel pumps Monday. If they need replacement, what do you guys think of these choices? Has anyone toyed with the idea of installing bigger injectors (964)?
Bosch Fuel Pumps - BoschFuelPump
Fully Enclosed FP34 044 Fuel Surge Tank, FP34 - 034Motorsport | Performance Parts for Audi, Porsche, and Volkswagen
Fuel Pump | Bosch 044 Motorsport | 3.8L RSR - GT2 Porsche Part Distributed By Patrick Motorsports