I have a bigun like that too. I've tried everything. Nothing works like the night and day everybody says. Nothing. Worst case was I ended up with a white chalky corrosion like residue on everything. Best case was it came "kinda clean". It just sits on the work bench now.
I had a friend get one with the same results. To test them you can submerge a straight sheet of aluminum foil and it should start eating holes in the foil. His changed the appearance of the foil but no holes.
