I have a 2000 S4 (6 Spd, 125k mi) that's throwing multiple DTC codes. I was driving to a friends house in 6th gear when the car went into EPC/Limp mode. I would say that I sometimes drive "spirited" but I don't rag on the car. I checked the codes that showed up and got these:

17743 - Engine Torque Monitor 2: Control Limit Exceeded
P1335 - 35-00 - -

16487 - Shareware Version. To Decode all DTCs
P0103 - 35-00 - Please Register/Activate


I shut down and cleared the codes and started it back up. It was running really rough and got this error:
16487 - Mass Air Flow Sensor (G70): Signal too High
P0103 - 35-10 - - - Intermittent

As I tried to accelerate, it kicked back to limp and the previous codes popped up again. Since then I've replaced the MAF (Didn't fix problem) and checked as much of the vacuum and intake systems that I could for leaks and tears. I'm at a huge loss here. I'm thinking it could be a possible 2nd faulty MAF but I'm not sure.

Add info: APR Stage 1 Chip, FK Coilovers, Forge Bypass valves, Samco TBB, K&N Drop-in, Short shifter, on 18" O.Z. Superleggaras.

 

Additionally, with the MAF disconnected the car idles normally and doesn't immediately go into EPC when driven. It sounds like the driver side wastegate is stuck open though and therefore won't build boost. I don't have a way currently of checking for boost pressure though. I'm afraid to drive it with the possibility of unevenly boosting the motor.

 

I was having almost the same issue as you, and would suggest trying the following

Look underneath your car where the intercoolers are
Check the two hoses that are underneath the car that goto the intercoolers, sometimes these will disconnect.
There is one by the oil filter and another on the exact opposite side of the car

This fixed the problem for me.
Good Luck!