Just cause that guy knows one vehicle, doesn't mean he knows another vehicle the same. Nothing against him though.
The proof is clear my friend. The 1GR responds EXTREMELY well breathing in and breathing out. It has been heavily restircted from the factory.
The thing about the URD Y than makes it the nicest, is that:
1 - it is 16 gauge 304 Stainless steel. (Strong)
2 - it is all mandrel bent, it doesn't have all of the kinks and reductions in size that bog down the flow.
3 - it bolts right up, and doesn't have any leaks at any of the welds.
1GRracer picked up about 30 whp and 20 wtq near the end of his rpm range. About 5700 rpms
Do this mod to the URD Y-pipe, if you have a 3" exhaust, and you will pick up even a little more hp/tq. http://www.xr-underground.com/vb3/showthread.php?t=42949