Mine was only held on by the one bolt (you already have that off as I see the tab) and the pressure fit of the tube in the hole. It has been a while but I think I wriggled it back and forth while pulling up and it slowly worked its way out. I would be gentle with a mallet as I have seen them bashed up... it is pretty thin walled tube.

I can't remember if the tube had an Oring seal on it or not. I know the Californian smog deal I removed did.