This is not a mod for 225 cars. Yes, I think the improvement from the pipe would be more...
significant when you are chipped, since the stock pipe can easily cope with the velocity and volume of flow required by the stock boost settings. I have read the same theory in EC. No idea as to the validity of the HP number, but it doesn't sound unreasoanble as a crank figure if you are chipped, and NS claims about the same.
Unfortunately, I did mine before chipping, so if it would have been more noticeable, I missed out on that, but it would require alot of testing ot prove that: stock pipe no chip, NS/ABD pipe no chip; chip with stock pipe, chip with NS/ABD pipe.