yes, maf defines what the o2 sensors should see, fuel gauge reads, vvti functions, and throttle operates. it's kind of a big deal in the IS, also important that you try and keep stock location and stock diameter piping for CEL free operation.
with a standalone, the MAP controls injection and ignition, but the maf is necessary for EVERYTHING else... that's why not many people can completely go standalone, how it's all ridiculously tied together.
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LC SSI 006