Jay have you ever put on a set of headers that excited the exhaust port in a more straight out shot? When we dynoed my 545 we used my headers that are in the car as they are bigger than the ones Ron has but we put them on upside down and it made good power 700+. Of course when installed in the car they have to be put in correctly and on the dyno at Car Craft meet this summer I lost way more than I thought I should have. I can attribute some of that to the weather and drivetrain loss. I was so disapointed that on Friday night I went over to Grove Creek to see if it had slowed down or something. But it ran just fine as usual. And one more point my headers are not near as turned down as some of the pipes on your dyno set. just a thought.
