The normally-aspirated (N/A) 2ZZ-GE motor is somewhat short of torque!
The OEM manifold uses a short, small-bore (38mm dia) primary set feeding into a large-bore catalyser pipe with an internal splitter-plate forming a rudimentary secondary pipe. A 4-2-1 design - even Lotus realised they needed that lay-out to maximise what torque there was on offer.
This 2bular 4-2-1 manifold for the road cars has a much-improved design, with stepped primaries into a pair of matched-length secondaries. The pipe diameters are crucial for best performance and combined with fabricated/TIG-welded merge collectors, gains of 15bhp and 12ft/lbs of torque.
The connection to the 2bular 200cell catalyser uses the OEM cup/gasket design