Performance loss from headers to HP manifolds

I did have 3.91 gears in it and it really went well, to the tune of 12.30@115 mph. But I got tired of the high rpms crusin on the highway so the 3.21's went in it. I called the Comp Cams tech line about what kind of cam to use with the stock manifolds and he said that the XE268 has enough exhaust duration to do the trick and that it was basically designed with that in mind. He did not recommend another cam to use and even stated that it would be good with the NOS. So there you have it, something that I never thought about. This has been a real good thread as far as all opinions are expressed and the learning never stops. Any input is always appreciated. Thanks guys!