You really can't measure an exhaust at the collectors - If I measured a set of extractors I have for a Holden 186 we'd be looking at near 3 inch diametre - I can tell you now the exhaust isn't anywhere near that big down the line!! I'm 99% sure that's also the "old thinking" with extractors is to make the collector area larger for "ALL" the exhaust gas to meet up at. Max power is about making the exhaust gas move down the pipe the easiest way possible - the exhaust pipe needs to work like a chimney, help draw the gasses out.
What we're doing is making them collide for that "thump-thump" sound. I'm hoping it's all in the extractors for 90% of that subi beat - My thoughts are to build a set of these extractors and keep the 2 inch "cat back" (really it's a "Y pipe back") system that's already there. If that's not sounding decent then start playing with mufflers. Of course this is unless my exhaust builder says he knows something that'll be heaps better for the note
Also was meant to ask you Willy, has the not changed at all since the initial build? Exhausts seem to have a tendency to kind of bed in/change note as they wear a little bit. I know Ruby's exhaust is different to how she sounded when they were first fitted...
Cheers
Bennie
