Well, I went ahead and checked the duty cycle despite getting 6v (55%) with KOEO. From what I could find out, it should be 70%, 85%, 100% so I'm not sure what's going on with that. The reason why I'm interested in the duty cycle is because the exhaust smells rich, the fuel economy is pretty poor (200 miles on full tank!), and because the previous owner apparently messed with the lambda screw.

Anyhow, once the car warms up, I get a fluctuating reading between 5.5 and 6.5 volts (51-58%). At 2500rpm, I get around 8.5 and 9.5 volts (28-36%). This is a bit out of the "acceptable" 10% deviation, but I haven't adjusted the screw yet because I'd like to make sure that I am in fact checking duty cycle and not something else due to not being able to get into test mode.

Any thoughts, hints, etc would greatly be appreciated. Thanks.