Question: I have to delete list item but not able to do due to some permission issue : 
1. Ribbon
2. Powershell
3. Information Policy Management 
4. Logging through site collection admin / App pool account

Unable to see the permission for item through "Manage Item Permission".

Any other way to delete item.

Answer: 
You have to create a separate view for this. You can mark it as hidden if you don't want users to see it.

I experienced the same issue, and this seems to be the only work around.

By the way, if you investigate how SharePoint manages list views deployed to separate pages, you will see exactly the same behaivor: a new view is created and marked as hidden, and then any new changes are applied to this view.

The code:

```
// list - SPList object

var newView = list.DefaultView.Clone(list.DefaultView.Title, list.DefaultView.RowLimit, list.DefaultView.Paged, false);
newView.Query = @"<Where><Leq><FieldRef Name='DateTime'/><Value Type='DateTime'><Today /></Value></Leq></Where><OrderBy ><FieldRef Name='Modified' Ascending='false' /></OrderBy>";
newView.Hidden = true;
newView.Update();

var xlv = new XsltListViewWebPart();
xlv.ListName = list.ID.ToString("B");
xlv.ViewGuid = newView.ID.ToString("B");
manager.AddWebPart(xlv, "Rich Content", 0);
manager.SaveChanges(xlv);

```

(this exact code was not tested, but it is based on the 100% working code we use in production)
You can add the view at the time of instantiating the webpart rather than looping through all webaprts on the page and finding the webpart you need.
Also your query seems to be incorrect, try removing Where clause from the query. You may also find this [link](http://sharepointnadeem.blogspot.in/search/label/XSLTListView%20Webpart) useful.