[Shotimes] Semi-O/T: vulcan running rich

[Jon Heese]

Pardon the OT, but I believe my '95 Vulcan is running rich and I'm 
curious if anyone has any ideas of what might be causing it.  I used to 
get 25-30 mpg out of her, and now I'm only seeing 15-20 on the highway, 
and her exhaust smells like I'm dumping money out of the tailpipe.

The only noteworthy thing about it is that the rear bank cat clogged 
about 2k miles ago, and I removed it and replaced it with a straight 
pipe.  I suspect that the cat died *because* of the rich condition, so 
I'm hesitant to think that it has anything to do with the cause of it. 
I'm not thrilled about the imbalance in backpressure between the two 
banks (it's on my list to fix), but would that cause it to run rich?

My list of possible suspects (in order of likelihood in my mind) are O2 
sensor, difference in backpressure between banks confusing O2 sensors, 
and the MAF (I've got a spare I can try).  I'm not particularly fond of 
the change-everything-out-until-it's-fixed auto repair technique, but 
I'm not sure how to narrow it down any other way.  So, anyone have any 
ideas for further diagnosis?

TIA,

Jon Heese