i think your base String should look like this: base: DELETE&http%3A%2F%2Fstaging.xxxx.com%2Fapi%2Fmodel%xxxx%2Fcontroller %2F2467&oauth_consumer_key%thekey%26oauth_nonce %3D1429%26oauth_signature_method%3DHMAC-SHA1%26oauth_timestamp %3D1260804448%26oauth_token%3Dtoken%26oauth_version%3D1.0
so you had to strip out _method=delete and send via POST but the basestring must start with DELETE maybe this helps Volker
