Belanger Headers question

[King RT10]

If you add belanger headers to an already installed cat back system on a Gen 2 (corsa cat back)
what would be the hp gain? I am guessing 20hp to 25hp.
Would it be more with an S/C installed?

 

[STUGOTS]

Yes it would be more with a S/C.

Belanger claims 50 hp for the headers alone but the most anyone ever saw that I know of is 30

 

[FE 065]

BTR Performance guarantees 50hp when using their Belanger headers and catback on non-creampuff Vipers (with no cats).

 

[BigCarrot]

I didn't get anywhere close to 50.