Is intercessionary prayer prohibited in Jodo Shinshu (Japanese Pureland?)

Taitetsu Unno is a modern day Shin master. In his book "River of Fire, River of Water" he explains the concept of the Japanese equivilent of the concept of "suchness" which is called sono-mama or kono mama simply meaning life "as is" or "just right as it is" through a popular Shin poem:

You, as you are, you're just right, Your face, body, name, surname, For you, they are just right.

Whether poor or rich, Your parents, your children, your daughter-in-law; your grandchildren, They are, all for you, just right.

Happiness, unhappiness, joy and even sorrow, For you, they are just right.

The life that you have tread is neither good nor bad, For you, it is just right.

Whether you go to hell or to the Pure Land, Wherever you go is just right.

Nothing to boast about, nothing to feel bad about, Nothing above, nothing below.

Even the day and month that you die, Even they are just right.

Life in which you walk together with Amida, There's no way that it can't be just right.

When you receive your life as just right, Then a deep and profound trust begins to open up.

I think it's clear that the acceptance of things "as they are" is very important in Jodo Shinshu. You are not trying to pray for things to be other than what they are. This sense of acceptance is a concept which is understood in other Buddhist traditions as well. But it is beautifully expressed in this poem, I think. :)

Intercessory prayer is viewed as, at most, superfluous to the practice of Nembutsu. Practically, Amida is seen as unlimited in his power and scope. Maintaining the Mahayana teaching of sunyata (non-duality), there is no separation between "I" and "Amida". He knows our minds precisely (maybe more) than we do, and feels our suffering as his own. As a limitless Provider (as Oya), he knows what we need and gives freely, just as children don't have to beg for good food from a good parent (Reference for this teaching below). So, in this way, the practice is redundant.

From "Prayer and Nembutsu" by Rev. Shoko Masunaga is Minister of the San Mateo Buddhist, Church San Mateo:

In the Shin doctrine prayers are not rejected since they come from the hearts of men and women who are weak and ignorant of the Law [of Cause and Effect]. But Saint Shinran finds that prayers of supplication and petition, asking forgiveness for the sins, are not necessary in the life of a Shin follower. This is because Amida Buddha, the Highest Truth, is not a God, a creator of the universe, a being who stands outside of man and the world, or the power that judges the action of man. Rather, Amida Buddha is the living compassion, free from all limitations, and living in the Highest Truth, Oneness. Amida's compassionate actions are directed to all beings in order to free them all from the world of illusion and ignorance and lead them to Pure Land. His actions and desires are in accordance with the Highest Truth. His power is so great and his aims are so clear that there is no limitation attached to his compassion. It is the absolute-non-discriminatory compassion, directed to all, just as the sun's rays pour light upon this world without discrimination. No supplications or prayers are needed on our part since the heart of compassion is the prayer of Amida that all will be safely directed to the Pure Land. Man is being uplifted, embraced, even when he is falling deeper into the cycle of birth and death.

(Source URL: http://seattlebetsuin.org/prayer_and_nembutsu.htm)

Saying that, individual followers may act spontaneously, voicing dharmic aspirations as reminders for our limited selves, not to "persuade" Amida to act this way or that.

Reference: Naturalness: A Classic of Shin Buddhism by Kenryo Kanamatsu