if the manifold's buggered you could use e34 530i/535i ones instead, they fit the e30 better! cast, but still flow well - andy's still using the standard e34 manifold and running 250bhp ish...
tubular manifolds are still cool though!
think there might be problems with a 6 branch m30 manifold clearing the steering shaft in an e30 though
i put e34 535i manifolds on my e28 engine, a better solution for the e30. the port shapes were the same. then i went back to the same chap 3 months later and bought the rest of the engine