Dippy, sorry about that, I had stuff over my head here when I read your first post and didn't figure I was expected to give some input
IMHO yours and Jonny's aren't running too bad, the only issue that I see with your numbers (Dippy) is that IMHO you're running way too much boost for what the K03s can take reliably and efficiently in the long run... 1.35 Bar means very high exhaust backpressure (because of the K03 hotsides being so small and restrictive), which will lead to an engine that will detonate much easier than on lower boost, so this would be a normal explanation for your car running very low ignition timing on full boost.
I must now say that I have done a few more runs on Shell 98 RON on my car yesterday (was going for a few beers with DaveP in Brussels) and I have lost 0.3 of a second because of getting 6 degrees <beep> on full boost, my first run (the one that's posted) had been done on Total Excelium 98 RON, and IMHO that juice rocks in Belgium.
Dippy, if you want to find out more as to why your engine is holding back, log knock sensor CFs in channel 020, if they are pretty high, that is half of your answer. IMHO an S4 can do around 340-350 HP with a very free flowing exhaust by running very reasonable boost, the boost I'm running now (same as when I posted the first FATS run) is 1.2 Bar absolute peak and tapering to 0.8 at redline. Too much boost will make the engine flow lots of air (high MAF) but the problem is that when the engine flows that air but can't get it out through the exhaust (backpressure), you won't make good power, and that sort of power is also something that's not going to last for very long if you really have it (280g/s at ~6000 RPM being about 380 BHP)....
HTH,
Mihnea