O2 sensor

[cwagner at info2000.net]

I am currently running a EFI setup using a GM TBI unit and a 7747
computer.  I purchased a chip from Howell for a 258 cube. inch 
engine for my 77 Toyota Land Cruiser.  The engine is stock other 
than the EFI.  The problem is the engine runs rich and uses quite a 
bit of fuel.  I don't have the money to purchase a scanner to see 
what the computer is doing, so I disconnected the EGO sensor to 
mess around with it to see why the rich mixture.  During idle, the 
reading on a DVM is almost zero.  Any other time it is around 600 
mv.   From what I have read, this indicates a rich mixture but the 
computer doesn't set a code for a rich mixture.  I drove around with 
the sensor disconnected and never got a code for a lean O2 sensor 
reading which seemed weird.  Does anybody have any ideas?
Also, this is the first time posting anything here, so any ideas 
about how to go about posting are welcome.