The stock carb had a flat spot when the air cooled off after I went to eat, I noticed coming back Thursday night w/ new  Supertrapp pipe on for 1st time.
It backfired big (about a .38 special or 9mm) and had a flat spot just as it came off idle and was slow to rev up.

So I installed the new carb tonight along w/ a K&N filter.
http://www.icestormcity.com/elsnod/bigcarb.JPG
Current config;

157.5 main jet
5C17 needle
X-6 needle jet
white washer reduced to .050 from .088
67.5 pilot jet under diaphragm

The #4 washer's O.D. was too big for the recess in the slide and was binding, so we just filed the white nylon washer down to 50 thou.
I set the idle screw to 3 out, by the book.
My compadre said 'this thing is gonna run like S%#t and you're gonna wind up w/ the stock one back on it'.
I put the big new carb on the bike & as much as I had changed I was surprised, relieved and very happy it cranked at all
In fact Suzy fired right up and idled real good w/o  any choke!

Crack the throttle and it barks, and falls right back to idle, unlike the old one which fell below then back up.
I rode down 1/2 mile  to I-240, up to about 80mph over to next exit about 1/2 mile  and back home, about 3 miles around town. No malfunctions. She pops a little on decel and sometimes as I shift up, but no duck and cover stuff now.
Throttle response was good around town.
I will need to ride it w/ this set-up more and maybe try a 155 main later.
Next need to pull the tank, check the valves and stick a new plug in it before I test top speed.
It's getting late so better not be blasting around town any more tonight. 8)
Gotta say thanks to Greg and everyone here, and at LS650.net http://www.heise-workstations.de/ls650/LS650.html
TheThumper page http://www.thumperpage.com/ and the
Be _Savage folks http://autos.groups.yahoo.com/group/Be_Savage for all the tuning and carb input, oh yeah I got the carb from our new sponsor at Anderson Vintage Parts too.

P.S. I did a snorkel-ectomy to the air box too.