I haven't built a lot of these but I do understand the attraction of fitting a Rotrex supercharger to the 1.6Ltr 1ZR motor for more power and torque. Looking at the spindly factory manifold you really need to get rid of it and fit this 2bular bigger-bore 4-1 design to cope with the extra gas-flow. Reducing back-pressure also reduces the stresses on the supercharger itself. Doesn't have to work so hard pumping all that air! I use a stepped primary pipe and a proper 4-1 merged collector - all TIG-welded for integrity and cosmetics!
I always use the very high-quality German manufactured HJS HD (High Durability) 200cell catalyser in all my exhausts. This is the latest Euro 6 version - meets very strict emissions tests World-wide and ultra-reliable! I have had problems in the past with Bosch Lambda sensors and after a lot of testing settled on the NTK sensor - more expensive but it works. An exhaust catalyser depends for its life on the correct operation of the 1st Lambda sensor. Don't settle for anything else - HJS HD catalyser + NTK Lambda sensor!
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