Engine building can be a complex and time consuming and a process that once complete will not need attempting again on that engine for years to come.
Part of that process apart from the exhaust and this
Inlet Valve is ensuring the correct gaskets and
Valve stem seals are used for replacing the old items. Be sure and only use high quality OE and none OE parts you can find them all here at CMS.
Try this pro-workshop gasket seal - 08C70K0234M - for a more professional result. Don't forget to order all the vale springs, collets, Valve stem seals and gaskets required when reassembling the engine.