Can anyone tell me if thay use or used fullsac pipes to convert to full duals. You can see the site at fullsac.com.

 

I have the fullsac tru dual conversion on mine. Works fine for me.

 

I have the fullsac conversion complete with their cores in my original mufflers. No issues with anything. Highly satisfied.....

 

While the current Delphi EFI system is quite capable at picking up some of the changes encountered when altering the way the engine breathes, changing the type of exhaust system really necessitates EFI tuning changes.

See http://i33.tinypic.com/1zps6lu.png where I took the last SERT software and generated a set of graphs showing the VE table tunings between the stock touring exhaust and dual pipes. I placed the common low value in one 0-throttle corner and the common high value in the other 0-throttle corner so all the colors in all the graphs would represent the same values.

Even if you don't understand what you're looking at, you should be able to see how the "topography" differs between the two systems. These represent relative airflow values the EFI uses to calculate how much fuel to spray at different combinations of engine speed and throttle position. While the system can largely accommodate the changes while running closed-loop, the open-loop areas will not be treated correctly. (you'd be safe in considering the top quarter and right-side quarters of those graphs being "open-loop" but it's much more complex than that) And in making the accommodations, the EFI's (limited) "autotuning" functionality will be used up at worst and at best operating outside of its range center. I would neither run my engine that way nor recommend others do so. Pick up a TTS tuner and get it right.