I'm a detailer by hobby and i must be honest, i don't get the point of all these fancy shampoos. As far as i'm concerned, the shampoo is there to lubricate the sponge/washmitt and nothing more, shampoo is really only capable of removing surface dirt, bugs, tar and other contaminants need specific chemicals to remove them imo. I use Simoniz Ultimate Wash & Wax and it's very foamy and slippery and cheap from costco too.
Maybe my car never get dirty enough to put my shampoo to the test tho. Try and wash it every week/two weeks which is usually around 400 miles/week