Can you run your car with the headers open one time? that will tell you if you will see an improvement. other wise your just doing it for the sound, which i think is cool.
I'm running a 416 with 1 3/4 hookers thru 2 1/2pipes w/H and Dynomax super turbos dumped at the axle. I installed 3" manual cutouts. I see between .15 to .2 improvement in ET an about 2mph gain with them open.
After 2 years of crawling under the car to open them I added the electrics last week! I love them, can't wait for the first cruise nite.
