Note: Not currently available. There is a delay in the manufacturing at this time due to volume of work at Piper Exhausts. If you require one urgently please advise.
The stock down pipe has a flexible mid section that can fail prematurely. In addition the stock part is made with several compromises. The bends are poor with kinking thus reducing bore diameter, which is not good for a good gas flow. The two into one section causes a restriction and the lambda sensor port is often restricted due to poor manufacturing techniques/mass produced methods.
The oval section flexi section also flattens the inlet pipe thus causing a restriction! Aftermarket ones are even worse with proven power losses and changes the sound of the exhaust!!
My new design uses mandrel bent stainless steel tube and good component design. The improvements are better flow rates and performance.
The troublesome flexy section has been replaced with the same section we use on the 4.2.1 manifold making it an easy job to replace the flexy section but also can be upgraded with the 421 at a later date thus saving money and gaining power and torque!
The design takes the two pipes from the manifold under the sump before converging into  the Y piece collector. This design increases both torque and BHP . 
Considering some aftermarket SS ones are around the £250 mark and O.E ones circa £140 my new design is very competetively priced so don't bother shopping around!!