I have been wondering the same. I would certainly like to have one with a little more lift and some changes in duration.
Not sure how much top end I would want to give up but I certainly would like some more low end grunt. Cams are a good answer for our engines. Unfortunatly I don't seem to be able to find a performance vehicle that has aftermarket support that uses this engines. Not a lot of minivan owners puttin cams in, lol.
I have been searching and have not seen anything yet and I don't see anything that would work in ours. IN addition, I don't have a way to tune for them so I am not sure how much of a benifit would be seen by putting in a cam without tuning for the changes....
bah