There have been a lot of threads that give the impression that the IPD unit doesn't give much performance advantage over the stock twin downpipe manifold. Other headers give better results if you want performance.

I'm not enough of an authority to get into theory but some of the the B20 builders say unless you have a pretty hot motor the stock B20 manifold does a good job.

Grassroots Motorsports and Classic Motorsports have done two projects using B20's and neither used the IPD header although they did use other IPD-sourced stuff.

Just throwing the info out there in case you were wanting to improve performance with your exhaust choices.

Best regards,

-Mario E.