Yes, your syntax is incorrect there. And you already have it in intID, so just re-use it
doc.Load("http://api.something.com/1.0/products.xml?q="& intID &"&CategoryId=163")
Alternatively, you can use String.format. Not sure on the exact VB syntax, but something like this:
doc.Load(String.Format("http://api.something.com/1.0/products.xml?q={0}&tdCategoryId={1}", intID, catId))
I hope this helps