I know cars drop revs. But this thing was dying, no two ways about it.
I have not seen an RB with such an issue yet. I can assure you none of my Rb25s (or mates RB20s) have come anywhere near dying when removing the cap, nor is there any real "choofing", and as for oil, one or two splatters on the cam cover only.
The S15 was in a different league, and yes, thats a different league to the other S15's I checked. A friends S15 checked the very next day seemed to have a nice choof, but would idle, and not splatter oil everywhere. The S15 I checked was litterally blowing oil out, not splattering it.
IMO thats excessive. Also noticable on shut off, the engine ran on, which I saw as a sign of low compression in the cylinders.
Everyone has different ideas on blow by and what is 'excessive', but I'm happy I walked away from that one! I won't be touching one again in that state either