Hi Rene -
My headers started life as "Hall Big Bore" headers. They have 1 7/8" primary tubing, but we cut out the (crappy) "merge", installed a much improved stainless band clamp between the headers and tailpipes, and then upgraded the stock tailpipes to 2 1/2" all the way back to the stock Ansa cans.
Even with these mods, I might suggest there may be better header / muffler solutions that could provide increased performance.
(Rumor has it that / I have heard anecdotally) the Hall headers are a boat design. The best thing about them is the clearance of the engine bay and suspension with no, or minimal mods to the stock tailpipes and mufflers.
There are no "collectors" per say - only the 4 tubes coming together at the same spot. I am convinced there is more horsepower in my engine wanting to get out, stifled by my exhaust configuration....
That being said - "better is the enemy of good enough" - I'm not in the market at this time for a new exhaust (in both Euros, or time).
Here's a link to the exhaust portion of my thread...
5357 Exhaust Upgrade
Here's a picture of the "merge" and the flange from the Hall Setup... that HAD to go...
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