sx needs help

When they changed my engine the new it came with this manifold. it looks completely different but gives me more low-end torque than the old one.
I have no idea what car they got it from

You are a lucky owner of a jap-spec engine!
Its a original engine for the s13 ca18det in Japan.
If you go higher than 300 bhp its going to be restrictive.

yup the jap engines got the 8 runner intake manifold controlled with an extra set of butterflys.

if you glance at the motor (and if you not looking for it) you wont see the differences between the motors!