Both Summit and Jegs have the Pypes 3" to 3" and 3" to 2.5" collectors. 304 stainless, tig welded. Reasonable price. I see no possible explanation for necking down to 2" and even less reason to open back up to 3". Once you've necked down for more than 6-8", it's like putting a cork on the exhaust.
We've done countless dyno tests. If you have nice TTI headers and 500hp, we would recommend a 3" to 3" collector, 3" X pipe, 3" mufflers and 2.5" tailpipes. All mandrel bent which is a MAJOR factor in choosing this consideration. If a local shop, did this same configuration, you'd lose 30-50hp. :(
