I'm a chevy guy, had quite a few 4.3L V6's over the years, worst was the 95's with the CPI injection systems. I had two 95's and threw everyting in the book at them, always had rough idles, one even had an occassionally miss that never showed up on scanners/codes assurances deces. It is wierd that the V6's were rough, but the V8's run smooth as the 4.3L was a 350 with 2 cyls knocked off. I did have a 350 in my camaro that ran rough though, oh wait, that would have been due to the larger cam
Our '05 liberty does seem to run a little rough, maybe it's just the nature of the beast to say.