Yep I noticed this when I removed the regulator. I kept my timer set to the same time and almost had an empty tank when I landed. I normally have around 3-4 ounces to spare. I think the reason is that I had to set the engine so rich to keep it from leaning out at the end of the tank. Also it had to be rich so it would not lean out in a vertical upline or hover. There might be other reasons too but the fact is that it definitely used more fuel without the regulator.