As I work thru this issue, I'll keep updating what I find out.

From the GPU-README file:

Q: My scrypt hashrate is high but the pool reports only a tiny proportion of
my hashrate?
A: You are generating garbage hashes due to your choice of settings. Your
Work Utility (WU) value will confirm you are not generating garbage. You
should be getting about .9WU per kHash. If not, then try decreasing your
intensity, do not increase the number of gpu-threads, and consider adding
system RAM to match your GPU ram. You may also be using a bad combination
of driver and/or SDK.

When I change the intensity from 20 to 9, my shares goes from 0 to 134 and rising.
Temp. rises to 100C!

I greatly appreciate the forum in assisting me in getting my mining rig with 3 HD 7950s up and running.

When I logged into BTC Guild and started mining two days ago, my PPLNS shares were 278, 298, 542, 576, 334, 262.
My 7950s were running at 100C and getting 1.2MHash. So I read the forum threads on cgminer.conf and tweaked mine.

I changed my cgminer.conf to:

 "intensity" : "20,20,20",
"vectors" : "1,1,1",
"worksize" : "256,256,256",
"kernel" : "poclbm,poclbm,poclbm",
"lookup-gap" : "2,2,2",
"thread-concurrency" : "22272,22272,22272",
"shaders" : "0,0,0",
"gpu-engine" : "0-1100,0-1100,0-1100",
"gpu-fan" : "0-85,0-85,0-85",
"gpu-memclock" : "0,0,0",
"gpu-memdiff" : "0,0,0",
"gpu-powertune" : "0,0,0",
"gpu-vddc" : "0.000,0.000,0.000",
"temp-cutoff" : "80,80,80",
"temp-overheat" : "75,75,75",
"temp-target" : "65,65,65",
"api-port" : "4028",
"auto-fan" : true,
"expiry" : "120",
"gpu-dyninterval" : "9",
"gpu-platform" : "0",
"gpu-threads" : "2",
"hotplug" : "5",
"log" : "5",
"no-pool-disable" : true,
"queue" : "1",
"scan-time" : "60",
"temp-hysteresis" : "3",
"shares" : "0",

With this config, my fans are running smooth (62C), my hash rates are good (1.7).

However, my new PPLNS shares have decreased to 4, 2, 1, and a lot of 0.

Is that just a coincidence?

Or does changing cgminer.conf effect BTC Guild PPLNS share rate?