It sounds like the transmission shift control cable is binding. That's the one that goes from the throttle spool to the transmission. There are instructions in the 700/900 FAQ for checking it out. That is typically the problem with the sticky shifting (and delays cause hard shifts under light throttle with the AW transmissions).

I'd check the fuel pressure regulator for leakage too, if you're looking for rich mixture issues. Is the diagnostic unit giving you a code that indicates a rich mixture?

With the turbocharger, you might be seeing a little bit of oil residue or unburnt fuel. The turbo's pipes usually are a little bit on the dirty side after some miles, as compared with the naturally aspirated engines. The tailpipe doesn't indicate mixture problems necessarily. I wouldn't worry about that, or the 02 sensor unless you're having specific problems and a code from the engine computer that indicates trouble.
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Chris Herbst, near Chicago, IL. 93 940, 91 240, 90 240, 88 740, 87 240