I just happened to be out with my buddy who has an 00 Si (in Canada its called an SiR, same car though, 1.6L 160hp DOHC VTEC) and we have the same bolt ons (intake, exhaust). His car has 110 000Kms and my 01 ITR has 80 000Kms, we both drive the hell out of them but also never miss any oil change or scheduled maintenanace. For the forty horsepower he's giving up to me I barely pull away from him (my car works perfect BTW). Its only noticibly faster in the last 1000 or so RPMs before shifting. The ITR should definetly be faster though. If the one you drove wasn't properly maintained then it probably doesn't work 100%