Yeah, I suppose knock sensors would be of some help

. The E36 uses the DISA manifold though, so I would imagine that the ECU is programmed to deal with:
a) controlling it
b) is tuned for the two distinctly different running modes. The fuel and spark maps are likely quite different than ours (with pieces of maps for the two different intake states...determined by RPM I believe).
There may even be feedback to the ECU to tell it if the internal flap has malfunctioned, so it may 'freak out' if there is not a flap connected at all.
Being tuned for the E36 manifold, just getting it running drivably with an E30 manifold (no turbo even) would be interesting. If you actually do try this, keep us posted. For your sake I hope am wrong if you do all that work! Maybe by then I will have finished cracking the 175 EPROM and some tuning can be played with.