Sure sounds like Mirna to me -- whoever it is has the crazy down pat.
The clue said the house is where the Grateful Dead lived one summer. The house turned out to be on Haight and Ashberry [sic] streets, then there you found your next clue to go to the Mint, then from the Mint to the finish line.
I think this would explain Chateau's
mysterious shot coming east on Oak St. Haight/Ashbury is close to Golden Gate Park so they had to backtrack back to the Mint, and from this map
Oak St. would seem to make sense. (Sorry to merely link -- I'm not so good with the pics.)
Oh, and there was a clue they actually had to "figger out"? And it wasn't shown? Sigh.
Also the hood of the mystery car is red, which doesn't match any cab the racers took from the mint (if it's a cab at all).
Could that be one of the Friendly Cabs that (IIRC) E/D and D/K took out of Oakland? I think an example is in one of Chateau's
shots -- it is red, white, and green, with the red as the top layer. It's not listed on that cool link to SF Cabs, but per it's own site
it's an East Bay i.e., Oakland not SF company. ETA: Some info about and a pic of the Greatful Dead house -- address is 710 Ashbury, a block south of Haight.