Dan Forey

Hello fella's, just wondering if you any of you can help, my JDM 99 STI version 5 ra limited edition has recently been booked in for a mapping session at Richard Henry Motorsport, I'm wanting to decat my car beforehand, the problem I'm having is my car has a Fugitsubo exhaust system, I've no idea if the down pipe is 3" all the way through, or it narrows to 2.5", am just wondering if any of you has had this before and knows the exact size before I purchase one.