well the stainless steel version of the budget header that is true equal length ( or atleast very very close) and has full burns merge collectors, and the correct secondary length and rear collector transition straight length, makes a good deal more than the normal budget header. This is on a pretty well built VE with a lot of money in it. That motor made about 7lb ft more TQ average from 5000-6800rpm and +8whp @ 7800rpm. That header was $1550. I am basing that mild steel price off of the stainless ones that I have built.
going with the final merge with a larger choke of 2.5" does kill power everywhere. you are merging sequential firing cyliders from 2" to a 2.5" size pipe... there is too much volume and this causes the exhaust gasses to expand too quickly and lose the directed flow path. Sort of like running a formed collector on a large 4-1 header. the gasses get "dumped" into the collector after the primary tube with no sense of direction to lead the gasses out.
The smaller choke ( or correct choke) allows the gasses to keep their velocity up as they merge and exit through the last collector. this helps pull a good low pressure on the collector after the last exhaust wave which helps scavenge gasses as well from the next firing cylinder.
Originally Posted by snickers 
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