I'm about to install some headers, plugs, wires, coil, remove AIR pump and EGR system. I would like to see how much HP is gained.

With the G-tech do you have to start off at zero mph the WOT to get the HP reading? Or can I be in third gear at 50mph? I ask because my car would have zero HP because it would just spin if I started in 1st gear WOT.

 

It's a standstill measurement. I remember doing it, standing still, set it up, it said "ready" then I hammered it in first gear until the redline, let off the gas. When you let off the gas, it goes to "calculating" and it gives you a readout. It told me 225HP when my car was stock.

 

you can measure it at any speed....just remember that due to wind resistance and lower gearing your going to get a lower reading at higher speeds. I measured mine from 60-75 or so and got a max of like 100HP.