Why not just run M and call it a day
I'm not the OP, but I like your idea! To cross-flash an M-box tune to an A-box (or possibly to an F-box), I assume I'd need to flash the whole eeprom as well as the tune, correct?
2000 S4 6MT should be A-box, but I'm not the original owner and this machine's obviously been tuned before (e.g., 17psi). The label is missing from my ECU, and I've been unable to read the eeprom (tried both the 1.31 and 1.40 versions of ArgDub's tool).
I took the chance (hoping it wasn't APR, etc.) and was able to read the flash BIN (attached) using the latest NefMoto app. I used TunerPro to do compare differences, and this BIN is definitely closer to stock A-box (342 different bytes) than stock M-box, but only 104 of those bytes are defined using the A-box XPF. The most matching definitions were 207 of those bytes using an F-box XPF, but unfortunately I can't find a stock F-box bin to compare.
My questions are:
1) What "box" is my current tune?
2) To cross-flash, is eeprom needed as well as tune? If so, where can I get the M-box eeprom to cross-flash to A-box (or F-box)?
3) For whichever box I have, is there an XPF available that would allow me to see all the variables needed for a rear O2 delete, for example? If not, is there a way for me to create a full XPF definitions file for whichever box I actually have?
EDIT: VCDS reports "8D0 907 551 A" (A-box), FWIW.
EDIT #2: Found a 551F bin on the S4Wiki and compared, and mine's definitely not that. I guess it's an A-box tune (BIN) after all, but the A-box XDF simply isn't as complete as the F-Box XDF. Need to learn more about these...