the DOHC has a problem with the infamous Oring leak. it is a port for when the block was designed for a distributor. the o ring fails and it is a PITA to replace. the best way to do it is to... well once you remove the intake manifold, and lower intake manifold, to clean the shaft as much as you can and then use quick steel epoxi or jb weld and seal it shut. RTV just doesnt work there. it will hold for about a month or two at most. i did the quick steel and it has held for 4 years now. the shaft you need to pull is basicly under the EGR on the block just under the rear head closest to the drv side. over on 60degreev6.com they have a write up i believe on fixing it. hope this helps.
