Who is useing Header extensions?

I used a program called" Pipe Max" to determine my collector length.
As was said above it's measured from the inside of the header where all the pipes merge. I ended up with a 12 inch extension on the header.
Did it help.......Yes a few hundred on the 60 foot, but that was when i had my 3000 stall. now i have a 4200 stall.
Agree, the more stall you have, aka the closer you are to your torque peek, the less it will show up in a 60 foot or et.

Remember that your o2 sensor will not read correct at idle. you will need several more feet of pipe past the sensor, to get it to read correctly at idle