Bought a wideband o2 and did some testing

[Brent Meints]

So is that for 91 octane California fuel?  I have 93 octane here and often
find 94 octane and with a JWT ECU we dropped a wide band on it and adjusted
the fuel pressure down about 3 psi to get a 12.4volt reading.  I haven't had
any problems, though I haven't ran hard in anything hotter than 85:.

Brent

for pump gas its more like 10.5-11:1.  12.5:1 would be
a really aggressive tune for a full race turbo car on
C16.

Mike