I searched through all the posts on this subject but couldn't really find any information that helped me.......I just finished my H22 swap and the intake manifold I am using doesn't have the IAB plate......I do notice that after a while of idling and on occasion when coming to a stop light after running for a little while my idle starts to "surge" up and down a little bit.......can this be caused by no IAB plate......and other than this are there any PROS / CONS to not having it on there......Thx

 

Your surging idle probably isn’t caused by the lack of an iab plate.
The most likely culprit would be your iacv.

As far as running without the iab plate…
Theoretically you would lose a little bit low end torque and gain a bit high up due to fewer pumping losses but that would all depend on the actual resonant tuning of the intake.
Throttle response should be better without the plate though.

It would be interesting to see what the dyno numbers would be on the same engine with the iab plate and then with the plate removed.
This would be the only real way to verify the effect of running without the iab plate.