Just saw a topic on KCTAU about it , here is the details :

Xyz Materials
Monsters that are used to Xyz Summon are called ‘Xyx Materials’, and are placed underneath the Xyz Monster, to show that they are attached to it. Monsters that have become Xyz Materials are not treated as cards on the field. When an Xyz Monster leaves the field, all of the Xyz Materials attached to it are sent to the Graveyard. If an Xyz Monster is flipped face-down, or becomes controlled by the opponent, the Xyz Materials are not sent to the Graveyard. They remain attached to the Xyz Monster.

Leaves The Field
Some monsters have effects that activate when they ‘leave the field’. For example, these effects activate when the monster is sent to the Graveyard, or is banished, or is returned to the hand or Extra Deck. When a monster on the field is shuffled into the Main Deck, or becomes an Xyz Material, it is no longer a card on the field, however its effects that activate when it ‘leaves the field’ will not activate.”

full read : http://www.yugioh-card.com/en/rulebook/YGO_RuleBook_EN-v8.pdf

I have something to say: HAHAHAHAHAHAHAHAHAHAHA to the imbecils that bought Tour Guides (no offense to anyone >_>)... well.. that's why they didn't ban Sangan in this banlist, they made this when they started seeing the Tour Guide--->Sangan abuse ._.

so when does tengu gets his effect ? when he's attached or when he is ditached ?

Tengu does not get his eff at all if used as Xyz material king007, its pretty well said there.

Pro rule is pro.

i couldn't belive what was said lol that's why i wanted to check

So they finally switched to OCG's rulings, thats good and crumbles some strategies here as Tou Guide Agents that had the overwhelming advantage of Tour Guide + Sangan opening play to fetch Veiler or whatever they need.