2" vs 2.5" intercooler piping

I recently had my turbo starlet on the dyno and tested back to back 2" vs 2.5 cold side Intercooler pipes of the same shape/ design.

At 14psi it made 150kw at the wheels with the 2.5" inch pipe. Using the 2" there was no differences anywhere more than 1kw.

Interestingly it picked up 4.9kw retarding the cam timing 3 degrees for a total of 154.9kw (stock N/A cams)

Interesting stuff, Ive been wanting to do some back to back testing on stuff like this!

I wonder if the result would be the same with a bigger turbo?! Didn't WRC cars run 2" tubing?!

Youre only as strong as your weakest link...your cold side piping wasnt your weakest link...