Helix Flex-Section Uppipe
The very best bang-for-the-buck performance modification for your scooby. This uppipe yields a 15+ whp gain simply by eliminating the restrictive pre-cat. By eliminating this pre-cat (with only a minor impact on emmissions) faster turbo spoolup as well as significant top-end gains are achieved. Additionally, not only does the flex section absorb torsion caused by hard driving, it eliminates leaks by allowing flanges to seat properly! Furthermore this uppipes eliminates the possibility of your pre-cat breaking away and destroying your turbo over time (has happened before!).
The Helix uppipe features:

• -High quality double layered flex section - Reduces torsional vibration on vital exhaust components and turbo, also ensures perfect seal (even with aftermarket headers, downpipes, etc.)
• -Thick 1/2" 304 Stainless Steel Flanges - to prevent warping and reduce heat expansion
• -304 Stainless Steel Mandrel Bent Piping - Ensures proper flow and durability
• -CNC Machined EGT bung - seats EGT properly unlike competitors which will eventually leak. (The EGT is there for a reason!!) -2.25" piping diameter - optimal for upgraded turbos
• -includes OE style gaskets (from same factory as OEM gaskets)
  
  Please note that an aftermarket uppipe is a good modification on the 02-05 WRX only. The 06 WRX and the 05+ STI both have catless uppipes.