necking down after collecter?

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. :(

I got the Summit pre fab exhaust system they sell. They just need to weld it up. The TTI headers came with the 2" extensions/collectors. The header exits 3" but the extension it came with goes down to three. I think that is where he got confused. They do pretty good work otherwise. I guess he was cornfused. lol? I guess I should have Flanagan look at it after it's all said and done see if he can improve it a bit.