Ok, I think I have the side pipe's settled.
Now, how about the different brands of collectors and styles
Merge (venturi) Collectors-
This is from Car Craft.
" Merge collectors are typically built on a custom, one-off basis by specialists, making them very expensive (in the neighborhood of $1,000 or more a pair). However, at the recent SEMA show, we ran across Dynatech Headers, a small, race-oriented header builder that makes the closest thing to a mass-produced merge collector on the market. Dynatech's merge collectors, available in high-temp coated mild steel or stainless steel, are still not cheap at around $600 for a pair, but at this price level, we felt it was worth a test to see what this technology is all about".
A brief note of testing-
"To keep the test simple, we ran both collector styles without mufflers to eliminate that variable, and we made no tuning changes beyond verifying that timing and carb jetting were optimized for each setup.
The results of our test were impressive. With the standard collectors, power peaked at 517 hp at 6,300 rpm and 475 lb-ft of torque at 5,000 rpm. With no other changes than slipping on the merge collectors, power increased to 528 hp at 6,300 rpm and 482 lb-ft at 5,000, a gain of 11 hp and 7 lb-ft of torque at the peaks, and more testing would likely improve on this. Finding more than 10 hp with a simple bolt-on in an engine already making nearly 1.5 hp per cubic inch is truly remarkable in our book".
Great results but, $600.
There has to be a cheaper way.
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