I installed a K&N Cold Air intake on my 08' 4.7. Not many retailers advertise the K&N fitting the 2008 4.7, but instead, just for the ealier year WK 4.7's (the Gen I). I found that Summit Racing however did represent that it would fit the 08'. I ended up buying the CAI from AutoAnything becuase they had the best price with free shipping at the time. AutoAnything charges a high restocking fee (if I remember correctly) for returns becuase something does not fit. They guarantee fitment and they were saying that it did not fit my year/engine (even though Summit racing did say it would fit).
Also, I consulted with the K&N website. Also they do not have the polished metal tube Cold Air intake advertised as fitting the 2008 4.7 (check it out).
So I took the chance and ordered figuring (hoping) Sumitt to be right and in the worse case scenario, I could make it fit.
So I followed the instructions and things for the most part were the same as expected. Remove factory air box, intake, etc. The first main difference I noticed was that the instructions called for removing the vacum resovoir from the airfilter box. Mine did not have this on the airfilter box (step 14 of the instructions). There was also a vaccum hose that connected to this resovoir (it was removed in step 4 of the instructions).
Next, the "air plenum" as it is called, did not have any bolts securing it. It was attached via rubber connector. You simply have to pull it off (step 20b and 20c).
Next, if you go to step 29, it instructs you to remove the T fitting and route it to the nipple on the intake tube. Mine did not have a T fitting. I instead had a vaccum hose that was connected to the lid of the factory airbox. I had unplugged that hose when i removed the factory airfilter box. So now I had a vaccum hose running up to where the airfilter is, but nowhere to tap into. I disconnected the vaccum hose from its source, sepoerated it into two pieces (one is plastic the other rubber) and renstalled the rubber portion, now tapping into the nipple on the K&N tube. this was the connection that would have been used, but I did not have the T-fitting as per the instructions due to variance in motor design between model years. You can see in the last picture that i drew a line to this connection.
Sorry about the few pictures. the How-To was a bit of an after thought on this one becuase I figured there are hundereds of write-ups on CAI's. Then it occured that this was a bit unique. I also attached the instructions I am refering to.
Here is the product I used in the 2008 4.7:
The arrow is pointing to the connection I was talking about above.