I'd also have a look at the intake manifold gasket. Replace if in doubt -- will set you back about $6 and one hour of your time. It's a good idea to replace it anyway, if it's original and thus 15 years old (shrug :).

The throttle body gasket may also be worth replacing (about $4).

I don't know about injector seals. Mine are original brown color ones and still don't leak a bit after 11 years, save for one which was mechanically damaged. Maybe other people were unlucky with them -- mine look almost like new, save for the carbon deposit on their bottom side. There's no cracking of any kind on them, and they are nice and soft. Strange, but true. I'm pretty sure they weren't replaced by the PO.

Cheers, Kuba