Yes, the plenum must be removed to change spark plugs on the V6 but it's easy-pesy.
1) Disconnect 4 hoses from plenum (one on the throttle body, one on the rear passenger side of plenum, one of the left side middle and one on the right side middle.
2) there is a plug to a sensor on the rear drivers side of the plenum that must be unplugged.
3) unplug plug from throttle body
4) remove 6 bolts and it slides right out.
You should be able to remove the plenum in 5 minutes (10 minutes for first timers).
Be very careful when removing the two hoses on the sides of the plenum. That is hard plastic so it would be easy to break and expensive to replace. I insert a flat blade screwdriver between the hose and the plenum and wiggle the screw driver to break the initial seal then pull it out by hand. Because the hose extends about 4 inches into the plenum I don't fully remove it , instead I leave it loosely in the plenum so when I remove the plenum they naturally slide out. When installing the plenum I rest those hoses back into the plenum first so the they naturally slide back in as the plenum is slide back into place.
There are 6 bolts you must remove not 5.
There is one bolt all the way back towards the firewall that must come out.
So the bolt pattern on the top of the plenum is as follows:
1 short bolt up toward the front of the plenum
4 longer bolts in the middle of the plenum
1 short bolt at the rear of the plenum (i believe this is the one you havent removed yet)
That bolt is a bit more difficult to remove due to it being under the engine bay ceiling. What I do is take a short socket (13mm I think) and put it on the bolt, then I take my smaller ratchet and connect it to the socket that is already on the bolt and un-tighten the bolt.
Once you break the initial tightness of the bolt you should be able to remove the ratchet but keep the socket on the bolt and use your fingers to turn the socket the rest of the way. The reason you may want to do it this way is because if you attempt to unscrew the bolt completely with the ratchet still on it you will not be able to remove the ratchet, socket or bolt due to it will be pressed against the ceiling of the engine bay so you won't have the room to remove it.
2008 G8 V6: Eibach lowering springs, 18" staggered rims, K&N CAI, Series 4400 Flow Master axle backs with FlowMaster tips, radiator cover, tinted tails, silhouette of G8 third brake light.
Last edited by mrathell; 03-12-2017 at 09:17 AM.