Some of our forum tuners have chimed in on this topic. I think they could help us out a lot more.
- How many tunes are sold in CA vs. other states? I bet it is higher in CA on a per car ownership basis.
- What are they really tweaking? Is the timing advance riding an already fine razor edge WRT octane?
- I'm sure no admissions of guilt will be made here, but I firmly agree with the point that tuners ARE almost never engineers (at least not in a relevant domain) and likely don't understand some of these subtleties as well as they should.
- SFP - perhaps you can expand your work reaching out to those with failures and get some private, non owner identifiable data about who did and did not have a tune?