The normally aspirated (N/A) 2ZZ-GE motor is somewhat short of torque! The factory manifold is a small-bore (38mm) primary set into a large-bore secondary pipe with an integral splitter-plate forming a rudimentary secondary-pipe. Even Lotus knew they needed a 4-2-1 on this motor!
This 2bular 4-2-1 manifold for the road cars has an improved layout. Stepped primaries, with a bigger bore into two merged collectors greatly improves flow and scavenging at the cylinder head. The secondary pipes have been lengthened to match the primaries and along with their big-bore merged collector improve the power and torque all the way through the rev range.
All hand-fabricated/TIG-welded - gains of 15bhp and 12ft/lbs are typical.