I thing Dougs headers are modeled after the TTIs and are less expensive. They have a large "Dougs" logo welded to one of the top tubes though. Looks super ugly. If that doesn't bother you then that's an option.
I have TTI headers and it seems a lot of folks on the forum use them. Fit well and headers don't belong in the same sentence. LOL
Since Dougs (Est 1960) was making headers long before TTI (Est 1988) thought about it maybe TTI modeled their headers after Dougs.....