Removing sparkplugs:

WARNING: This page is about a different car, the 2002 Volvo C70, 2001 Volvo C70, 2000 Volvo C70, 1999 Volvo C70, and 1998 Volvo C70. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Identifying Camshaft Components

Courtesy of VOLVO CARS OF NORTH AMERICA.

Remove:

any charge air pipe over the engine.
Seal the openings.
the upper camshaft belt cover.
the cover over the ignition coils.