Confirmed. Looks like MaxQuantity is being ignored. The X headers should not get passed on the URL, they are HTTP headers. Each has a URL equivalent (e.g. OPERATION-NAME instead or X-EBAY-SOA-OPERATION-NAME). They are for use with SOAP requests and are not needed with REST calls. I'm surprised you're getting any results at all, but apparently eBay is string processing to get the parameters because **&Z-ZZZZ-SOA-OPERATION-NAME=findItemsByCategory** works too. That could stop working at any time.