Sounds like they don't want to do it rather than can't. PelicanParts have a step by step guide with photos of how to remove the inlet manifold.
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(Starting at Figure 30)
i haven't done it on the 2.8 yet myself, but I followed the guide for the 1.9 (Figs 1-29) and it was daunting but entirely possible
BMW Z3 Intake Manifold Removal and Replacement | 1996-2002 | Pelican Parts DIY Maintenance Article
Time to replace your intake manifold gasket? It's easier than you think! Don't believe us? Read on!
www.pelicanparts.com
(Starting at Figure 30)
i haven't done it on the 2.8 yet myself, but I followed the guide for the 1.9 (Figs 1-29) and it was daunting but entirely possible