Under my knowledge the d15b7 timing is supposed to be set to 16 degrees, + or - 2 degrees if necessary. As the guy said above. Some models have additional notes on how to set the timing. Like on my car I have to jump (with a paperclip) the service connector under the dash to prevent the ECU from adjusting the timing while I'm doing it manually. This takes the computer out of the loop and allows an un-conflicted adjustment. The 15 degrees you set it to should be fine.
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