Do Agnostics Tend To Be Perceivers? I don´t know, but it´s interesting to contemplate the concept whether or not MBTI has any correlations.
If I were to examine the issue I would not look at the letter P. Using my own personal experiences as a comparison, I´ve noticed that as I age (I´m 42) I am more sure about some things and ¨decided¨. However as a consequence of experience, my exposure to new and different things has increased the absolute number of things I need to consider and has illuminated my own inability to truly ¨know¨. Consequently I believe any correlation, if there is, between MBTI and agnosticism, must also be take into consideration other factors like: age, gender, nationality, et. al.
In that vein I would suggest taking into consideration cognitive functions. Specifically Ti vs. Te. If I were a betting man, I´d say you are more likely to find a correlation there. Taking that one step further, Ti Perceivers.
I´d also like to add one more thing, these self labeling systems and the evolving terms to go along with them, are social & political constructs. I think this is relevant to the question because social acceptance can be a bigger deal to some ¨types¨ than others.
FTR I am an atheist INFP.
Good luck on your inquiries.