My apologies if this is answered elsewhere, but searching didn't find exactly the answer I need.

I have a P0601 code on my '02 A6 2.7T (MT6) with Revo trial firmware (flashed about 4 years ago).  Audi dealers say the ECU needs to be replaced (at $1400), but that's as accurate as the IT guy saying to replace your motherboard.  The thing is, this error came out of nowhere, 4 years after I had the ECU flashed.  I'm hoping the flash or EEPROM just got corrupted in normal operation, instead of the EEPROM really going bad, and that flashing "good" firmware will fix it.

Questions:
a) Can the trial Revo firmware (I've read it can mess with EEPROM) be causing the P0601 to show up spontaneously?
b) Since I don't have the stock firmware (never read it before Revo trial was installed), can I obtain working firmware from somewhere else?

Note:
The car was running fine after the code, although I'm getting some very bad engine skips now, like a misfiring spark plug, which may be completely unrelated.  Also, the Audi dealership says they also read EGT errors (which I don't see on a basic OBD2 reader), and that those errors are unrelated to the ECU.  They're saying I need to replace both sensors for about another $1400.  But I don't trust that.

Note-2:
I've been an embedded software / firmware engineer for 20 years and written assembly and C for ~20 different microcontrollers (and reverse-engineered object and binary code).  But with family and busy job, I don't have a lot of time to dedicate to this.  So hopefully I can handle whatever needs to be done quickly. 

Thanks!

Rosstech:
http://wiki.ross-tech.com/wiki/index.php/16985/P0601/001537

Could be low voltage, but I'm not convinced, you'd have had other low voltage codes too.

Like DD said though, Revo embed their stuff into both, so you'll need both files..

Bit weird for it to show after 4 years, so it could well be low voltage.  Get yourself a Rosstech cable; or even cheaper (like 15 quid), a chinese copy!