I want no text flowing on the sides. I tried setting width to full - but the graphic does not center - stays flush left.
Unfortunately you've not given any details on how you're placing the graphic (<ig>, <igt>, pickup?) or any of the parameters that you're using.
Assuming you're talking about a pickup, since you mention about wanting no text flowing on the sides, I tried a quick test using a pickup.
On the pickup itself (type: here) I have Width: full, Scope: page or block (doesn't seem to matter for my sample), Keepout: fs.
In the pickup I have an annotation block and a graphic block.
On the annotation block I have Xorig: left and that text block is flush left.
On the graphic block I have Xorig: center and the graphic is centered.
Perhaps you've set width to full on the graphic block but not on the pickup itself?