Does that rule out a mixture problem?

Not entirely, IMO. But I wanted to suggest another possibility, based on there being so few reported problems with the CIS ECU and system in general (maybe one here in the past couple of years).

Reviewing this long thread, I'd suggest:

1) getting a temp sensor reading from ECU pins 9 and 11 to rule that out

2) cleaning the IAC valve (search or see 700/900 FAQ for methods) or swapping in another one

3) clean throttle body

4) set the base idle speed (ask for procedure in a new post, or get the Bentley 240 manual)

P.S. It may not be relevant, but unplugging the O2 sensor should not have raised the "cool" idle speed any, at least not in the first few minutes. Because the ECU doesn't look at the O2 signal until engine temp gets up to 65°. Before that, the O2 sensor is ignored (same as if unplugged).


--
Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.