Bro first of all Kar'cher Power washer does not come with the foam lance accessory. you have to purchase it separately from abroad or their service center here in lhr, islamabad etc can source this for you.
However nouman my friend, had that foaming lance accessory but recently he sold his karcher with that foaming lance, 
gussa to mujhay bi charha tha but he told me late that he sold that foaming lance too 
Regarding foam thickness, well there are separate shampoo/liquid to make it real like on youtube videos... with Turtle Ice shampoo, one can get foam but not much. i think 1 month ago Ustaad V-1 were using that foam lance on Rizwan bhai and shazoo bhai car, so u can browse older posts to check the foaming thickness and quality in those pictures.
if you see on youtube, they have some liquid kind of shampoo in it. However if you put pre-soak 1/5 diluted mixture in that foaming lance, then it does make real foam, tested by nouman. So i guess if we prepare diluted mixture of shampoo with water, one can attain better and thick foam.
Here is this accessory for 25$ seperate
Amazon.com: Karcher 2.641-848.0 Foam Nozzle: Home Improvement
