the Pre 1996 X20XEVs had a single path manifold too,
the dual tract just added a bit more low end torque, effectively giving you 2 differently tuned manifold in one.the dual tract manifold as fitted to the post 1996 X20XEV's and also the X18XE as fitted to the Vectra allow the low end torquo at low revs but as the revs increase the manifold pressure actuated a plunger to flip the paddles that you can see to allow a shorter inlet air flow path allowing more air to get to the cylinders quicker. It flips over at approx 3000-3500 revs from memory.
The cast aluminium one that has one flow or air may not be much better but its worth a try. I am sure I read on VVOC that there were gains to be found just by swapping manifold. Whether this is as a result of just having a cleaner inlet manifold or its due to the different style of manifold is yet to be found, but I am keen to give it a go.
The other interesting thing is that if no gains are to be had from switching the dual tract inlet to a single flow inlet on the X20XEV as its manifold is more efficient than the C18XE/Z20LET, then by power of deduction, fitting a dual tract inlet manifold to a Z20LET would prove benficial you would say. With forced induction and a dual tract giving a more direct air flow high up the rev range I would say that gains could possibly be had for Z20LET owners.

Koliko starijim XEV-ovima ? Da li je na veci B XEV 98smo ovakva (nisam zagledao )

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