89 s13 ka24e Rough Bogging during engine start @ Idle

[sil80tt]

During ignition, idle, its spikes then rapidly drops rpms from 2000s n lowers to about 0 then shuts off! After a couple of tries it turns back back on and idles fine. i Iv checked all my vacuum lines and they're all good but still hear a loud hissing coming somewhere along the Intake Manifold. Its coming from somewhere in the IAA so looked it up in the Manual but still cant seem to find out exactly where its leaking from? Any other ideas??



Thanx!