Rick,
One of the biggest problems with Cobras and EFI is the placement of the O2 sensors. They need to be a certain distance from the exhaust ports from the heads, and need to be hot -- even if they have internal heaters.
Is the SDS your ECU? Or are you running a Ford ECU such as an A9L or other EEC-IV-type processor. If a Ford ECU, I can recommend a guy at Dallas Mustang who's known as a guru (I'll need to dig up the name/info), but if not, then you may have to deal with the SDS folks.
Assuming that the SDS is the ECU, what are you using to tune it? Does it have any output capability so you can see if it's rich or lean, timing values, etc? If you do, that should tell you which direction to adjust towards. You could also get a lot of this info from a Dyno shop. Another option is to get a wideband A/F gauge ... don't waste your money on anything that says it'll work off a stock switching O2 sensor.
Another place to check for info is
www.diy-efi.org. You'll find tons of good info on their site, though I know that their server has been down for the past few weeks.
Either way, post some more detailed info on your setup and I might be able to save you from the tuning hassles I had in the early days.
Cheers,
-Neil.