Is there a taxi(MPV or mini van) to carry 6 pax from Pudong to downtown Shanghai? The cost?

There is no such a taxi holding six persons in the city. If you wanna share a van, you'd better reserve the pick-up service from your hotel (if you have booked one) or certain agency like Travel China Guide, whose contact is bookingtravelchinaguide.com.
Or you can share two taxis and it costs CNY150-180 per taxi.