We can discuss this 2012 rules change period. The easy part on the 1-4 and 2-3 pipes is that they are easily compartmentalized. Meaning it totally bolt/on stuff. No measuring or cutting.
Once you get to the collector it is more complex since this what I call the "cat pipe" since it when stock has collector, cat and runs back another 3 feet or so. These pipes are never stock any more from tip to tip because most of us remove the cat. Now way I did it was to remove the cat right near it weld (actually cat removed itself one day on track
![](http://944spec.org/944SPEC/components/com_kunena/template/default/images/emoticons/dizzy.png)
)and I had the remaining section re-fabbed. So my collector/cat pipe is still the same length and stock at the front and not at the back. Stock diameter pipe was used however.
So if we rule that the collector must be stock we need dimensions as to how far it needs to be stock. Clearly you are talking about the section from the 2 pipes to one, but how far after they join. 2 inches, 6 inches? One problem I don't want have is guys needing get new parts just because their cat deleted pipe joined the collect or 1" too close for the new rule.
So while the rule change make some sense, practical enforcement is important to think about. So far it has been considered "not worth the hassle", but maybe that needs to change.