I have one problem on mine and friends car with same setup. Both cars have K04 from RS4 with RS4 pre-turbo intake(only pipes from Y to turbo), fresh rebuild turbos. Injectors are from audi S3, no CATs and 3 inch downpipe
I can't get more than 320-330 g/s with 95% WGDC, both cars have new OEM N75 and new OEM MAF
I am not talking about MAF limit, only sometimes I hit it, but most of times there is a 310-320 g/s

I will post logs I must find them, but I think you know what I talk about,  is there anything else that is blocking engine to suck more air? Do we need bigger Y pipe, bigger hole on airbox?  

From my understanding stock RS4 have 320-330 g/s at 60% WGDC?

Here is my log, PS. don't look at fuel and ignition, car is running on WMI but not durring this log

way too many variables, intake restrictions, wg preload, n75, exhaust etc.

who knows?

going by MAF readings is maybe not the best benchmark anyway. How about just pure fats or rpm/sec comparos?

BW rates the K04's at 475 HP
http://nefariousmotorsports.com/forum/index.php?topic=20256.0title=

so you should be able to get more out from them.
I'd look into a hardware issue.