Ask and you shall receive. I just did this last month and I was more than pleased with the results!

https://www.performancetrucks.net/fo...d.php?t=465088

 

So I assume by FI you mean SC? Yes, if you pulley down and retune after installing the headers, you will be making gobs more power. As Sincal said, if you don't pulley down you will be making less boost on the gauge (the SC will be spinning exactly the same as before the headers), but getting the exact same amount of air into the cylinders (which is where the power comes from). You won't loose HP by "loosing" the psi number since you are still pushing the same amount of air at less pressure.

Boost is measured in psi, which is a measure of restriction rather than airflow. If the flow is held equal, and you increase the psi, you are likely going to make more power (given proper intercooling, fuel, etc.). However, if you increase the flow and let the psi drop, you won't loose power. Increase the flow and hold the boost steady (which means turning up the boost), you will be making lots more power (if you components can handle it).

 

Nice thread!