I have 2004 F150 5.4 with IMRC vac leak on right side. I forund it after doing a smoke test today. I cant really see exactly where it leaking other than the smoke was pouring out of this area. I am contemplating doing the repair myself but cant find any info or part numbers or diagrams. What is the most common problem causing vac leak on a low mileage truck (26,000 miles) and what parts possibly needs to be replaced?

All the info I have found so far is mostly talking about deleting the system. If you use the delete plates will the check engine light stay off? <!-- / message --><!-- BEGIN TEMPLATE: ad_showthread_firstpost_sig --><!-- END TEMPLATE: ad_showthread_firstpost_sig -->

 

Well, the Mustang guys remove them to remove a bit of restriction in the intake and gain a few pony's up in the rpm range. The trade-off is a reduction in low end torque.
I would keep them in a heavy truck. I would have to guess the leak would either be a shaft seal (more than likely since it doesn't seem to get driven much with only 26K on it) of the plenum gaskets.
I honestly have never had one apart, so I can not say for sure.