diff-maps

When a tuner modifies a file, they do not change bytes randomly — they change maps (the tuning tables). diff-maps compares a stock (original) file with a tuned file and answers the tuner's question: which maps changed, and by how much?

It is the map-level cousin of cook: cook diffs at the raw byte level and builds a recipe; diff-maps finds the actual tables and reports each one's change — max +23, avg +1.9, +18.3% — so you can audit a tune without a manufacturer database.

Think of cook as "what bytes are different?" and diff-maps as "which tables were touched, and how hard?".

When do I need it?

• Auditing a tune you did not make. See exactly which maps a "stage 1" file touched, and how aggressively.
• Checking a recipe explains everything. With --recipe, diff-maps tells you which changed cells the recipe covers — and which changes are untracked (extra edits the recipe does not explain).
• Reviewing your own work before flashing.

Try it (2 minutes)

openremap diff-maps stock.bin stage1.bin

  stock.bin vs stage1.bin

  1,985 tables found in stock · 1,990 in tuned · 342 matched pairs

  Map 0x000376F2   32×16   max +23   avg +1.9   +18.3%   Group A
  Map 0x002214D4   32×6    max  +8   avg +0.4   +12.1%   Group A
  ...

(Output shortened — by default the top 50 matched maps are shown.)

Understanding the answer

Every changed byte is accounted for somewhere: a matched map, a promoted changed block, or a "changed but not identified" region (flags, VIN, checksum stores — the kind of thing cook catches at byte level).

For developers

The same diff is one method of openremap.api — note the method name uses an underscore (diff_maps):

Where to go next