LF:2002 and Up Mini Van Sugesstions

I had the 3.4 in my camaro back in 95 and it ran very good up too 122k miles. I sold it to someone and its still running strong. Its not the most powerfull motor, but it held up good. I drove many highway miles. I've heard that the 3.4 dual overhead cam motor that they put in the Lumina eurosport or the z34 was a bad motor. I think that it was the heads though that were always bad. I always got close to 30 mpg on the highway. I know that its going to be different in the van, but I would think that it would be in mid twenties, just like the 3.8 do.