Will everything line up or will I have to do some modifying?
That 99/00 Civic Si IM (B16A2) will line-up and mount to the JDM B16A head.
And the fuel rail and everything will bolt right up?
Hang on to the spacers that go underneath. With the exception of how far off laterally the FPR is located on the fuel rail (not really an issue), all B-series fuel rails are pretty much interchangeable. Throttle boddy, IACV and IAT sensor are in the same locations between the two IMs and fit properly.
In short, it will work.
So the below one will work? This is the one that came stock on 99/00 Si’s.
Any intake manifold for a B16 will fit your B16 motor… That should be pretty obvious.
The issues you will run into (if any)will be vacuum hose routing.
well it’s kinda obvious but Honda could have changed some things in 11 years. Yeah my main concerns are the hoses and the fuel rail bolting up right.
Any B16, B17 or Integra/Civic Type-R Manifold will bold up to the cylinder head… the only things they changed are vacuum routing.
B18a/b and B20 will bolt up to eachother.
GSR are the ones that will only fit a GSR.
Edit
Right off the bat you’re going to have one extra BIG vaccum line… Either the one on the top of the manifold, or the one on the front. One is for the EGR valve, and the other is only used on OBD2 cars. You’ll have to plug that up with something… Or do it the ghetto way and use a section of hose with a bolt in it, then clamp both ends so it doesnt leak. You may run into a few other small issues like that on other hoses, but it should be relatively easy to work around.
The only way you’re going to notice a difference in power is if you have the OBD0 B16 manifold currently installed on your car, and are replacing it with the '99 manifold… After '93 (ish) they’re all prettymuch the same thing. The Type-R would be your best bang for the buck if you can find one for a reasonable price.