Both sets of test pipes are 1.25in off at the rear flange. I mounted the Z1 downpipes using the gaskets supplied in the rebuild gasket kit and torqued them to spec, all looked good until I bolted on the test pipes...the passenger side Z1 test pipe was off...I swapped it out with the SZ unit and ended up with the same misalignment. A good deal on downpipes isn't looking like such a good deal anymore...Spend the money on the good stuff folks.