I found that a .020" shim under my needle seemed to cure 
the sneezes/backfires/lean condition on the stock 800 
setup, and when I posted this to the internet, a few people 
emailed asking specifics on how to do this. They also 
mentioned not wanting to change pipes, etc. This got my 
curiousity up a bit. 

Since I was waiting on a set of full length heat shields 
for my Cobra Classic Slashcuts, I was back on the stock 
pipes. I'd been reading about the CV carb tuning procedure 
on the biketech website at 
http://www.nightrider.com/biketech/carbadjust.htm. They 
mentioned that you should idle the bike as low as it would 
go, then "tweak" the low speed needle for peak rpm, and 
blip the throttle. Open the needle in 1/4 turn increments 
until the bike no longer "sneezes", or some such. They
cautioned that poor fuel economy could occur if this 
proceedure isn't followed and the low speed circuit was 
unnecessarily opened too much. 

Since I've been cranking the screw out to 3 turns and 
letting it fly, and since I didn't really know when I'd 
reached the peak RPM range because one has to take so 
much stuff off of the stock setup each time to make the 
adjustment, I fabricated a remote method to adjust my needle. 

I then removed the .020" shim I'd stuck under the needle 
and re adjusted the carb's low speed circuit according to 
CV's recommendations. (By the way, my low speed needle was 
only backed out from "closed" 3/4 of a turn from the 
factory!!! Damn, I couldn't beleive it!). Wow...no backfires 
or sneezing. still a little cold natured, but once warmed up, 
she runs like a champ. With the .020" shim back in, I only 
need the choke to start it, then shove it in and go. I think 
that might indicate that it's a bit rich with the shim under 
the needle and the stock intake/exhaust, but I haven't run 
this combination long enough to look at the plugs. 

My "gut" feeling, based on CV's procedure and the results 
I got, the shim isn't necessary with the stock intake, airbox, 
and pipes. With my low speed needle set at 2 turns out, it 
idles and runs great into the factory pipes.

I think, for those with the stock setup, I'd knock out the 
plug on the carb that covers the low speed needle and crank 
it out to a couple of turns and ride. Maybe, the remote 
needle adjustment mod I made might allow you to tune it 
perfectly for your altitude, but I don't know how much 
affect altitude has on the stock system.