Im curious how much performance is gained by having one, and are they worth it even though the prices for one are really good anyway?

Yes, a Fastman is worth it, especially in combination with a CAI or open element intake, and better free flowing exhaust.

I definitely noticed the difference after installing mine, especially on the highway at higher speeds. Even though thats where I feel I gained the most, I can also feel a difference from a dead stop.

Worth every penny.

As far as actual numbers gained in HP, I have no idea. But even if they are only very slight, the increased acceleration more than makes up for it.

Its been so long for me that I cant remember what it was like before. I only drove my truck stock for about a month before I started putting work into it. I did get some track results from it though. Stock was 16.03. Ignition+openelement filter+throttle body got 15.7. 16.03 was done in november in 50 deg weather. 15.7 was done in march, 50 deg weather.

When you say a more free flowing exhaust, you mean like Magnaflow or Gibson? I have Flowmaster, and from what I hear, they dont "Flow" as well as some of the other brands.

I remember when I installed mine that I was impressed with the difference. I had my K&N FIPK installed before the Fastman TB and it was still night and day from the old TB.