INTP, Enneagram Type 5, or victim of Forer effect?

I don't know you very well. But I am getting a feeling about you. A special insight into your personality. Wait, it's coming...

You have a need for other people to like and admire you, and yet you tend to be critical of yourself. While you have some personality weaknesses you are generally able to compensate for them. You have considerable unused capacity that you have not turned to your advantage. Disciplined and self-controlled on the outside, you tend to be worrisome and insecure on the inside. At times you have serious doubts as to whether you have made the right decision or done the right thing. You prefer a certain amount of change and variety and become dissatisfied when hemmed in by restrictions and limitations. You also pride yourself as an independent thinker; and do not accept others' statements without satisfactory proof. But you have found it unwise to be too frank in revealing yourself to others. At times you are extroverted, affable, and sociable, while at other times you are introverted, wary, and reserved. Some of your aspirations tend to be rather unrealistic.

How close was I? Does that sound like you? Probably not, because you know that anyone who stumbled upon my blog (a selective group, in my defense) is going to read the same thing. But according to studies by the psychologist Bertram R. Forer people who are given this description of themselves - pulled randomly from an astrology column - rate the accuracy of the description on average as 4.26 out of 5 when they are told it's the result of their personality test given by an expert.

In the last few months I've been going through a bit of professional difficulty - painfully coming to a recognition that the career I've spent the last five years building isn't the right one for me. This has led naturally to a desire to analyze myself in various ways and get to know myself better.

First I found a book based on the Myers-Brigg personality test. After a lot of exploring I concluded I was an Introverted Intuitive Thinking Perceiver. Later, a friend forwarded me a link to a test based on Oscar Ichazo's Enneagram (based on a shape that's actually an enneagon), from which I concluded that I was a Type 5, or the Investigator. Of course, in both cases I took the cheapo free version of the tests, rather than the expensive "complete" version of the tests. I have no idea if the results would have come out different had I bought the full deal, and will likely not find out because I don't want to spend the money.

In both cases, the descriptions seemed to fit me perfectly. Here's an Enneagram type 5:

The perceptive, cerebral type. Fives are alert, insightful, and curious. They are able to concentrate and focus on developing complex ideas and skills. Independent, innovative, and inventive, they can also become preoccupied with their thoughts and imaginary constructs. They become detached, yet high-strung and intense. They typically have problems with eccentricity, nihilism, and isolation. At their Best: visionary pioneers, often ahead of their time, and able to see the world in an entirely new way.

And here's an INTP from Wikipedia:

INTP types are quiet, thoughtful, analytical individuals who don't mind spending long periods of time on their own, working through problems and forming solutions. They are very curious about systems and how things work, and are frequently found in careers such as science, architecture and law. INTPs tend to be less at ease in social situations and the caring professions, although they enjoy the company of those who share their interests. They also tend to be impatient with the bureaucracy, rigid hierarchies, and politics prevalent in many professions, preferring to work informally with others as equals.

And yet, perhaps because of my personality type, I was cynical and suspicious. So I did a little digging about enneagrams and quickly stumbled across a description of the Forer Effect, as described above. Essentially, when people are told that a personality type description is specifically for them they are quite inclined to believe it. This is encouraged by other delusions, such as cold reading,, community reinforcement, and selective thinking.

The case for the MBTI is a bit stronger, because originally I tested out as an ISTP, but it didn't sound quite right and I ended up going with Intuitive over Sensing. If the Forer effect was working in full, I'd have taken the first description hook line and sinker. But that doesn't necessarily prove anything.

So here's what I'd like to know: how can I test to see if I'm falling victim to the FE? Does the validation of others count for anything? What about the quality of the tests? A lot of big companies use MBTI; and supposedly the Enneagrams are popular with some Jesuits. I've searched extensively, but I can't find any FE innoculation, except for a large double-blind study, which unfortunately is a bit out of my price range right now. Any suggestions?