You very right to be, what cams did you have?
I pop'd along to an NPOC rolling road day at HiTech some years back, with panel filter, exhaust, decat, eBay header and afpr made 166bhp - just about normal compared to other SR20DE P11 the same day.
Few months later after swapping out the cams to Tomei poncams, ASP header and lightweight under drive pulleys with ignition advance and fuel pressure regulator optimised I gain 30bhp from the late visit. Same the combination of the cams and header just worked great. My brother who had a Corolla T Sport 190 at the time went back there in the week for a run, mods cat back and blitz panel filter made 189bhp which again is about pretty much bang on.
These hand built ASP headers were a thing of beauty.